ACIDS AND CHLORAMPHENICOL AS SANITIZING AGENTS FOR MEAT
CONTAMINATED WITH FOOD POISONING ORGANISMS

By
Choom phorn G o m u tp u tra

A THESIS
S u b m itte d t o t h e S c h o o l o f G ra d u a te S t u d i e s o f M ic h ig a n
S t a t e C o lle g e o f A g r i c u l t u r e an d A p p lie d S c ie n c e
i n p a r t i a l f u l f i l l m e n t o f t h e r e q u ir e m e n ts
f o r t h e d e g re e o f
DOCTOR OF PHILOSOPHY

D e p a rtm e n t o f B a c t e r i o l o g y an d P u b l i c H e a lth

1952

ProQuest Number: 10008313

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ACKNOWLEDGMENTS
The w r i t e r i s d e e p ly g r a t e f u l to P r o f e s s o r F . Vi. F a b ia n ,
D e p a rtm e n t o f B a c t e r i o l o g y an d P u b l i c H e a l t h , f o r h i s e n d u r­
i n g and e x p e r ie n c e d g u id a n c e i n th e c o u r s e o f t h e s e s t u d i e s .
To P r o f e s s o r L . J . B r a t z l e r , D e p a rtm e n t o f A nim al H u sb a n d ry ,
t h e 'w r i t e r i s l i k e w i s e g r a t e f u l f o r h i s i n t e l l i g e n t and h e l p ­
f u l a d v i c e . T h an k s a r e a l s o due to th e P a rk e and D a v is
Company f o r s u p p ly in g c h lo r a m p h e n ic o l used, i n t h i s i n v e s t i g a ­
t i o n . F o r e x c e l l e n t and p a i n s t a k i n g p h o to g ra p h y t h e w r i t e r i s
g r e a t l y i n d e b te d to M r. M. L . G ra y , D e p a rtm e n t o f A n im al
P a th o lo g y .

ACIDS AND CHLORAMPHENICOL AS SANITIZING AGENTS FOR MEAT
CONTAMINATED WITH FOOD POISONING ORGANISMS

By
Choom phorn G o m u tp u tra

AN ABSTRACT
S u b m itte d t o t h e S c h o o l o f G ra d u a te S t u d i e s o f M ic h ig a n
S t a t e C o lle g e o f A g r i c u l t u r e and A p p lie d S c ie n c e
i n p a r t i a l f u l f i l l m e n t o f t h e r e q u ir e m e n ts
f o r t h e d e g re e o f
DOCTOR OF PHILOSOPHY
D e p a rtm e n t o f B a c t e r i o l o g y and P u b l i c H e a lth

Y ear

A pproved

1?£2

Choomphorn Gomutputra

ABSTRACT

F o o d p o i s o n i n g s due to s t a p h y l o c o c c i an d s a lm o n e lla e a r e w o r ld ­
w ide i n d i s t r i b u t i o n , e s p e c i a l l y when S a lm o n e lla ty p h o s a w h ic h i s th e
e t i o l o g i c a l o rg a n is m o f th e ty p h o id f e v e r i s i n c l u d e d i n t h e S a lm o n e lla
g en u s.

P o r k a n d b e e f h a v e b e e n fo u n d to b e c o n ta m in a te d w i t h t h e s e

o rg a n is m s a n d a s u r v e y i n I l l i n o i s showed t h a t a s much a s 0 .2 p e r c e n t
o f t h e m a rk e t b e e f an d lli.,3 p e r c e n t o f t h e m a rk e t p o rk y i e l d e d
s a lm o n e lla e o n b a c t e r i o l o g i c a l e x a m in a tio n .
A s tu d y w as made to d e te r m in e t h e d i f f e r e n c e i n t h e am ount o f
g ro w th o f th e f o o d p o is o n in g o rg a n is m s o n t h e s u r f a c e o f raw l e a n p o r k
and b e e f ta k e n 1 cm b e n e a th t h e s u r f a c e o f r e t a i l c u t s , o n t h e a u t o c l a v e d
l e a n p o r k and b e e f , and on t h e s u r f a c e o f r e g u l a r r e t a i l c u t s o f raw
l e a n p o r k an d b e e f .

The r e s u l t s showed t h a t t h e g ro w th w as l e s s o n t h e

s u r f a c e o f r e t a i l c u t s o f t h e m e a ts due t o a n ta g o n is m o f f e r e d b y o t h e r
b a c t e r i a and t o d e s i c c a t i o n .
Raw l e a n p o rk and b e e f w ere fo u n d t o b e good m ed ia f o r t h e g ro w th
o f f o o d p o i s o n i n g s t a p h y l o c o c c i an d s a l m o n e l l a e .

E x p e r im e n ta l i n c u b a t i o n

o f t h e i n o c u l a t e d m e a ts a t v a r i o u s te m p e r a t u r e r a n g e s showed t h a t t h e
o rg a n is m s i n c r e a s e d t o l a r g e nuiribers a t 1 5 .6 - 3 2 .2 C (6 0 -9 0 F ) .
The p o r k r i n d and t h e e x t e r n a l f a t c o v e r in g t h e b e e f c a r c a s s w ere
fo u n d t o b e p o o r m e d ia f o r th e g ro w th o f t h e o rg a n is m s a t v a r i o u s
te m p e r a t u r e r a n g e s .
E x p e rim e n ts w ere p e rfo rm e d to com pare t h e g e r m i c id a l e f f e c t o f
t r i c h l o r a c e t i c a c i d , d i c h l o r a c e t i c a c i d , d e h y d r o a c e ti c a c i d (s o d iu m s a l t ) ,

Choomphorn G om utputra

m o n o c h lo r a c e tic a d .id , a c e t i c a c i d , and c h lo r a m p h e n ic o l on t h e fo o d p o is o n ­
in g o rg a n is m s on l e a n p o rk an d b e e f .

The r e s u l t s show ed t h a t a c e t i c

a c id w as more g e r m i c i d a l th a n th e o t h e r a c i d s i n 1 p e r c e n t s o l u t i o n and
th a n 10 u g /m l c h lo r a m p h e n ic o l.
F o u r p e r c e n t v i n e g a r was fo u n d t o b e a p r a c t i c a l an d m ore
e f f e c t i v e d i p p in g s o l u t i o n t h a n 1 p e r c e n t a c e t i c a c i d i n d e s t r o y i n g th e
f o o d p o i s o n i n g o rg a n is m s o n th e p o r k an d b e e f .

The s o l u t i o n d i d n o t

im p a r t any a p p r e c i a b l e f l a v o r t o t h e m e a t s .
A m ethod o f s u r f a c e p l a t i n g t o d e te r m in e th e num ber o f s t a p h y l o ­
c o c c i an d s a lm o n e lla e o n a s e l e c t i v e and a d i f f e r e n t i a l medium r e s p e c t i v e l y
i s d e s c rib e d .

TABLE OF CONTENTS
PAGE
INTRODUCTION...................................................................................................................................

1

LITERATURE REVIEW.......................................................................................................................

3

G e n e ra l C o n s i d e r a t i o n .................................................................................................

3

S ta p h y lo c o c c u s fo o d p o i s o n i n g ...............................................................................

8

O rg a n ism s r e s p o n s i b l e ...................... ..............................................................
I n v e s t i g a t i o n s on g ro w th o f S ta p h y lo c o c c u s i n f o o d s ..................
E n t e r o t o x i n p r o d u c t io n b y s t a p h y l o c o c c i ...........................................
Sym ptom s....................................................................................................................
O v e rg ro w th o f fo o d p o i s o n in g s ta p h y l o c o c c i by o t h e r
b a c t e r i a i n f o o d s t u f f s ..............................................................................
A c tio n o f c h e m ic a l a g e n ts upon e n t e r o t o x i n ..................................
E f f e c t o f p h y s i c a l a g e n ts u p o n e n t e r o t o x i n ...................................
A n t i g e n i c i t y o f e n t e r o t o x i n .......................................................................
The c o n t r o l o f S ta p h y lo c o c c u s fo o d p o i s o n i n g ...............................

6
9
12
lb

S a lm o n e lla fo o d p o i s o n i n g ..........................

21

Im p o r ta n c e .......................................................................................................
Some o u tb re a k s o f S a lm o n e lla fo o d i n f e c t i o n ..............................
Foods a f f e c t e d and so u rc e o f i n f e c t i o n ..........................................
Some i n v e s t i g a t i o n s a s s o c i a t e d w ith S a lm o n e lla
i n f e c t i o n o f f o o d s .....................................................................................
The p r o d u c tio n o f " to x in "
by S a lm o n e lla .......................................
Symptoms................................................................................................................
The c o n t r o l o f S a lm o n e lla fo o d i n f e c t i o n ..........................................
E f f e c t s o f some common c h e m ic a ls on fo o d p o is o n in g
o rg a n is m s .........................................................................................................
PART I .

GROWTH OF FOOD POISONINGORGANISMS

15
16
16
17
17

21
22
25
27
36
32
33
3b

ONBEEF AND PORK...................

1R)

I n t r o d u c t i o n ............................ ..................................................... ...............................

^-6

T e s t o rg a n is m s ..............................................................................................................

b2

M edia u s e d ........................................................................................... - .........................

^3

E x p e r im e n ta l..................................................................................................................

b3

TABLE OF CONTENTS - C o n tin u e d
PAGE
R e s u l t s an d D i s c u s s i o n ............................ ............................................

52

Summary...................................................................................................................................
PART I I . EFFECT OF ORGANIC ACIDS AND CHLORAMPHENICOL IN SANITIZING
THE SURFACE OF BEEF AND PORK INOCULATED WITH FOOD POISONING
ORGANISMS..............................................................................................................................

68

I n t r o d u c t i o n .......................................................................................................................

68

E x p e r i m e n t a l................................................................................... ...................................

68

R e s u l t s an d D i s c u s s i o n ..............................................................................................

71

Summary..................................................................................................................................

7U

...........................................................................................................

82

GENERAL CONCLUSION....................................................................................................................

87

LITERATURE CITED.........................................................................................................................

88

GENERAL DISCUSSION

1

INTRODUCTION
W h ile fo o d p o is o n in g due to s t a p h y l o c o c c i i s c o n s id e r e d to com­
p r i s e a b o u t some n i n e t y p e r c e n t o f a l l fo o d p o is o n in g c a s e s i n N o rth
A m e ric a , Dolm an (2 7 ) p o i n t s o u t t h a t fo o d p o i s o n in g o u tb r e a k s a r e
n o to rio u s f o r u n r e l i a b i l i t y o f s t a t i s t i c s re s p e c tin g t h e i r in c id e n c e .
Inasm u ch a s m ary c o u n t r i e s do n o t p o s s e s s c h e a p an d r e a d i l y a v a i l ­
a b l e e l e c t r i c i t y and r e f r i g e r a t i n g e q u ip m e n t, th e in c id e n c e o f f o o d
p o is o n in g s h o u ld be h i g h e r , e s p e c i a l l y i n t r o p i c a l r e g i o n s w here th e
t e m p e r a tu r e i s n e a r e r to t h e optim um f o r . f o o d p o is o n i n g b a c t e r i a a l l th e
y e a r r o u n d , th a n i t i s i n t h i s c o u n t r y .

Many c o u n t r i e s i n th e F a r E a s t

u s u a l l y h av e t h e m eat s l a u g h t e r e d e a r l y i n th e d ay an d s o l d a s f r e s h
m e a t up to 2h h o u r s f o r b e e f , an d d u r in g a s h o r t e r tim e f o r p o'rk d e p en d ­
i n g on th e s e a s o n o f th e y e a r .

C o n s e q u e n tly much s i c k n e s s u n d o u b te d ly

i s due to c o n su m p tio n o f c o n ta m in a te d m e a t .
As w i l l be p o i n t e d o u t l a t e r , m a rk e t m e a t and m e at p r o d u c t s i n th e
U n ite d S t a t e s a r e b y no m eans f r e e o f fo o d p o is o n in g b a c t e r i a su ch a s
s a l m o n e l l a e , a n d , n a t u r a l l y , s t a p h y l o c o c c i w h ic h a r e u b i q u i t o u s .

F u rth e r­

m ore a c e r t a i n am ount o f m e at i s consum ed w h ich h a s n o t b e e n i n s p e c t e d b y
a t r a i n e d v e t e r i n a r i a n , a n d , a l s o , w i l d game w h ic h can n o t b e im m e d ia te ly
re frig e ra te d .
I t i s th e p u rp o s e o f t h i s i n v e s t i g a t i o n to d e te r m in e th e v i a b i l i t y
o f some fo o d p o is o n in g s ta p h y l o c o c c i and s a lm o n e lla e on th e s u r f a c e o f
b e e f an d p o rk a t d i f f e r e n t t e m p e r a t u r e s , an d a ls o to s tu d y t h e i n f l u e n c e

2

o f t r e a t i n g t h e s u r f a c e o f t h e m e at w i t h c e r t a i n common g e r m i c i d e s .

The

r e s u l t s s h o u ld d e m o n s tr a te t h e e f f e c t s o f r e f r i g e r a t i o n , o f k e e p in g
m e a ts a t v a r i o u s te m p e r a t u r e r a n g e s , an d a l s o o f tr e a t m e n t w ith v a r i o u s
a g e n ts o n t h e num bers o f v i a b l e b a c t e r i a o n c o n ta m in a te d m e a t.

3

LITERATURE REVIEW

G e n e ra l C o n s i d e r a t i o n
A c c o rd in g t o T a n n e r ( 8 9 ) , when m e at w as i n o c u l a t e d w ith p u r e
c u l t u r e o f b a c t e r i a w h ic h m ig h t b e e :x p ected to b e p r e s e n t i n s u c h a
p r o d u c t , i t s r e a c t i o n w as r e n d e r e d more a l k a l i n e .

A r e a c t i o n o f pH 6 .0

t o 6 .2 may i n d i c a t e i n c i p i e n t s p o i l a g e , b u t i t i s d o u b t f u l w h e th e r pH
m e th o d s c a n b e u s e d f o r d e te r m in in g t h e f i t n e s s o f m e a t.

The pH o f m e a t

d e p e n d s o n to o many v a r i a b l e f a c t o r s , s u c h a s a u t o l y s i s , r a p i d i t y o f
c h illin g , e tc .

F u r th e r m o r e , f o r some p e o p l e , c h a n g e s i n t h e m e at w h ic h

w ould a l t e r t h e pH

s i g n i f i c a n t l y w o u ld b e

th e s e r e a s o n s , s l i g h t c h a n g e s i n

pH c o u ld

c o n s id e re d d e s i r a b l e . F o r
n o t b e t h e o n ly m ethod u s e d

f o r ju d g in g t h e q u a l i t y o f m e a t.
T a n n e r (8 9 )
c a s e s o f a n a e r o b ic

s t a t e d *'S in c e s p o i l a g e

o f t i s s u e s , a p a r t fro m s p e c i a l

p r o c e s s e s , i s due to g ro w th o n t h e s u r f a c e o f th e

c a r c a s s , t h e b e s t p r o c e d u r e , a c c o r d in g to H a in e s , i s to make c o u n ts p e r
u n it o f s u p e rfic ia l tis s u e .

H is m eth o d f o r t h i s was a s f o l l o w s :

A s t e r i l e c o r k b o r e r i s p r e s s e d v e r t i c a l l y i n t o th e t i s s u e s t o a d e p th
o f one c e n t i m e t e r o r m o re .

By t h i s m eans a c y l i n d e r o f t i s s u e i s l e f t ,

a n d fro m i t s to p a d i s c a b o u t two m i l l i m e t e r s t h i c k i s c u t w i t h s t e r i l e
s c a lp e l.

The a r e a o f t h i s d i s c may b e com puted fro m th e d ia m e te r o f t h e

c o rk b o r e r .

M ic ro o rg a n is m s o n th e s u r f a c e o f t h e sam p le may b e b r o u g h t

i n t o s u s p e n s i o n b y s h a k in g v i g o r o u s l y w i t h g l a s s b e a d s and s t e r i l e s a l t
s o lu tio n .

When i t i s b e l i e v e d t h a t b a c t e r i a may h a v e p e n e t r a t e d , a

t h i c k e r d i s c o f m eat may b e t a k e n an d g ro u n d , o r d i s i n t e g r a t e d w ith a

k

m e c h a n ic a l s t i r r e r an d s t e r i l e s a n d . 11

" B a c t e r i o l o g i c a l m e th o d s p r o b a b ly

h a v e d i s t i n c t l i m i t a t i o n s i n r o u t i n e m e at e x a m in a tio n o n a c c o u n t o f t h e
tim e consum ed an d t h e f a c t t h a t m eat may a c q u i r e many b a c t e r i a a f t e r
p r e p a r a t i o n f o r t h e m a r k e t ."

" O r g a n o le p ti c t e s t s , l a r g e l y u s e d f o r f r e s h

m e a ts and s e a f o o d s , l e a v e much t o b e d e s i r e d . 11
W eaver (9 5 ) d e s ig n e d a t e s t w h ich show ed th e i n c r e a s e i n a c t i v i t y
o f h y d ro g e n s u l f i d e p r o d u c in g o rg a n is m s i n h a m b u rg e r s t e a k d u r in g th e
p e rio d o f in c ip ie n t p u tr e f a c tio n .

I t was p o s s i b l e b y u s i n g t h i s t e s t to

d e t e c t p u t r e f a c t i o n b e f o r e i t c o u ld b e d e m o n s tr a te d by o r g a n o l e p t i c
m e th o d s .

The m ethod o f t e s t i n g was s t a t e d a s f o l l o w s :

" 'P la c e o n e gram

o f m e a t i n a tu b e c o n t a i n i n g e x a c t l y 10 c c o f s t a n d a r d i n f u s i o n o r
e x tr a c t b ro th .
p lu g .

S uspend a s t r i p o f l e a d a c e t a t e p a p e r b e s id e t h e c o t t o n

I n c u b a te a t 37°C i n an a n a e r o b ic j a r Tinder p a r t i a l vacuum .

E xam ine and r e c o r d th e num ber o f h o u rs n e c e s s a r y to o b t a i n b la c k e n in g o f
t h e a c e t a t e p a p e r due to t h e p r o d u c t i o n o f h y d ro g e n s u l f i d e . "

He

fo u n d t h a t c o m p a r a tiv e ly good h am b u rg er s t e a k gave p o s i t i v e t e s t s i n
seven to te n h o u r s .

A t t h e tim e when p u t r e f a c t i o n becam e e v i d e n t b y th e

p r o d u c t i o n o f a f o u l o d o r , p o s i t i v e t e s t s w ere o b t a i n e d I n two t o f i v e
h o u rs.

He a l s o m e n tio n e d t h a t h a m b u rg e r s t e a k w h ich d i d n o t g iv e a

p o s i t i v e t e s t i n s i x h o u r s w o u ld k eep a t l e a s t t h r e e d a y s i n a good
re frig e ra to r.
I t w as fo u n d (8 9 ) b y e x p e r im e n t w ith lam b and m u tto n t h a t when
k e p t a t te m p e r a t u r e o f 6 0 -7 7 ° T1 t h e s u r f a c e b a c t e r i a c o u ld in v a d e th e
i n t e r i o r o f t h e lam b i n f i v e d a y s and t h e i n t e r i o r o f t h e m u tto n i n s e v e n
d a y s , b u t no b a c t e r i a l g ro w th o r i n v a s i o n to o k p la c e a t te m p e r a tu r e o f

2 -1 9 ° F .

5

The two m o st im p o r ta n t f a c t o r s w h ic h i n f l u e n c e d e v e lo p m e n t o f
b a c t e r i a o n m e at s u r f a c e s p r o b a b ly a r e t e m p e r a tu r e an d h u m id ity ( 89 ) .
G row th o f b a c t e r i a o n m e at s u r f a c e c e a s e s a t r e l a t i v e h u m i d i t i e s below

92 p e r c e n t , and b a c t e r i a grow w ith g r e a t r a p i d i t y a t t h e h i g h e s t a t t a i n ­
a b le h u m id ity o f 99 p e r c e n t .

However some b a c t e r i a l g ro w th was o b s e r v e d

a r e l a t i v e h u m id ity o f 70 p e r c e n t i n s t i l l a i r .

at

S e g a lo v e and D ack (8 0 ) fo u n d t h a t g ro w th o f fo o d p o i s o n in g s t r a i n s
o f s t a p h y l o c o c c i i s o l a t e d fro m fo o d p o i s o n in g o u tb r e a k s was n o t e v i d e n t
i n s a m p le s o f d e h y d r a te d m e a t c o n t a i n i n g 20 p e r c e n t m o is tu r e o r l e s s .
H ow ever th e y grew i n a l l th e m e at sa m p le s c o n t a i n i n g I4O p e r c e n t o r more
m o is tu r e r e g a r d l e s s o f s a l t c o n t e n t up to iw5>6 p e r c e n t .

The S . e n t e r i t i d i s

s t r a i n u s e d b y t h e i n v e s t i g a t o r s grew s c a n t i l y i n o n ly one p o r k sam p le
a t t h e lo w s a l t c o n c e n t r a t i o n o f 0 .2 8 p e r c e n t a d j u s t e d to 50 p e r c e n t
m o is tu re .

I n m e at sa m p le s a d j u s t e d to 60 p e r c e n t m o i s t u r e , g ro w th o f

e n t e r i t i d i s o c c u r r e d i n a l l b u t t h r e e s a m p le s o f h ig h s a l t c o n t e n t s
fro m

2 .2 0 - 3 .7 0 p e r c e n t .

The d e h y d ra te d sa m p le s w ere h o w ev er a u to c l a v e d

p r i o r to in o c u la tio n .
Many b a c t e r i a w e re fo u n d o n s i d e s o f f r e s h p o r k (8 9 ) p r e p a r e d
u n d e r l a b o r a t o r y c o n d i t i o n s , w ith a n a v e ra g e o f 2 x 106 and 160,000 p e r
s q . cm. r e s p e c t i v e l y f o r two b a tc h e s o f p i g s .

C om m ercial s i d e s o f p o rk

gave a. m ean c o u n t a f t e r c h i l l i n g o f 2 8 ,0 0 0 , a f t e r c u r in g o f 6 0 ,0 0 0 , and
a f t e r m a t u r a t i o n o f 106 o r more o rg a n is m s p e r s q . cm.
H a in e s ( 38 ) fo u n d t h a t l e a n b e e f h e ld a t te m p e r a t u r e s o f 0 ^ 0 ,1 C
( 3 2 . 0 - . l 8 F ) h a d a n a v e r a g e b a c t e r i a l c o u n t o f 14.0 ,0 0 0 p e r s q u a r e c e n t i ­
m e te r o f s u r f a c e a r e a .

W h ile v a r i o u s f a c t o r s a r e in v o lv e d i n c o n t r i b u t i n g m ic ro o rg a n is m s
t o b e e f , t h e c h i e f s o u rc e w as t h e h id e a n d h a i r o f t h e s l a u g h t e r e d
a n im a ls (8 9 ) .

T he m a in c o n ta m in a tio n i s b a c t e r i a l , p a r t i c u l a r l y a t 6 8 °F .

A t 3 0 .2 ° F m olds a n d y e a s t s may c o n s t i t u t e 35 p e r c e n t o f th e i n i t i a l
m i c r o b i a l p o p u l a t i o n on b e e f a f t e r s l a u g h t e r , an d a t t h i s te m p e r a tu r e
A c h ro m o b a c te r s p e c i e s h av e b e e n fo u n d to c o n s t i t u t e 90 p e r c e n t o f th e
flo ra .

The l a t t e r o rg a n is m s may c a u s e s l i m i n e s s on m e a t an d o t h e r s p e c i e s

o f b a c t e r i a may c a u s e r a n c i d i t y o f f a t u n d e r c o ld s t o r a g e .

The h ig h p e r ­

c e n ta g e o f c o c c i an d b i p o l a r o rg a n is m s may i n d i c a t e i n v a s i o n from, th e
r e s p i r a t o r y t r a c t and s k i n .
J e n s e n and R eeve (1[8) p ro v e d by s e r i e s o f e x p e r im e n ts t h a t th e
s t i c k i n g o p e r a tio n i n s la u g h te r in g hogs can in tr o d u c e s o u rin g b a c te r ia
i n t o th e c i r c u l a t i o n , b o n e s , and t i s s u e s .

T hey u s e d s t e r i l e k n i v e s , d ip p e d

s e p a r a t e l y i n t o c u l t u r e s o f C l o s t r i d i u m s p o r o g e n e s , C lo s tr id iu m , f l a b e l l i f e r u m , C lo s t r i d i u m m u ltif e r m e n t a n s , and. B a c i l l u s "p r o d i g i o s u s , t o p lu n g
i n t o t h e n e c k i n th e u s u a l m anner a f t e r th e s k i n h a d b e e n p r e v i o u s l y d i s ­
in f e c te d th o ro u g h ly .

A f t e r th e h o g s w ere a llo w e d t o b le e d i n th e r a i l f o r

t h e s t a n d a r d tim e (1 2 m i n u t e s ) , t h e n d ro p p e d i n t o

s c a l d i n g v a t and p a s s e d

th r o u g h a l l o p e r a t i o n s , i n c l u d i n g 2lj h o u r c h i l l , th e b a c t e r i a c o u ld be
r e c o v e r e d from, v a r i o u s p a r t s o f t h e b o d y , e s p e c i a l l y t h e bone m arro w ,
i n th e m a j o r i t y o f c a s e s .

They c o n c lu d e d t h a t m o st p r im a ry b a c t e r i a l

c o n ta m in a ti o n o f p o rk r e s u l t s from t h i s o p e r a t i o n .
B re w er (U) , i n h i s w ork w i th th e b a c t e r i o l o g i c a l c o n t e n t o f m a rk e t
m e a t s , c o n c lu d e d t h a t :
1 . C o u n ts from d i f f e r e n t s a m p le s o f th e same c u t s o f m e at
u s u a l l y v a r i e d m ore th a n th o s e from d i f f e r e n t m e a ts .

7

2 . P r e p a r e d m e a ts u s u a l l y c o n t a i n e d m ore b a c t e r i a t h a n
fr e s h m e a ts .
3 . Smoked m e a ts c o n t a i n e d a much s m a l l e r num ber o f b a c t e r i a
t h a n f r e s h m e a ts .
U. O f t h e b a c t e r i a e n c o u n te r e d i n th e d i f f e r e n t m e a t s t th e
c o lo n g ro u p p r e d o m in a te d .
The a p p e a ra n c e o f f r e s h m e a ts c o u ld n o t b e t a k e n a s an
in d e x t o i t s b a c t e r i a l c o n t e n t .
B a c t e r ia d e v e lo p q u it e s lo w ly on b e e f a t f i r s t ( 8 9 ) .

D uring t h i s

l a g p e r io d th e y are d e v e lo p in g on s o lu b le n itr o g e n o u s s u b s ta n c e s a lr e a d y
p r e s e n t on th e b e e f .
d e v e lo p r a p i d l y .

A f t e r a l a g p e r io d o f some UO hou rs a t 9 8 .6 °F th e y

8

S ta p h y lo c o c c u s f o o d p o is o n in g
O rg an ism s r e s p o n s i b l e
S ta p h y lo c o c c i i s o l a t e d fro m fo o d p o is o n in g o u tb r e a k s w ere e n t e r o t o x i n p r o d u c in g .

Some o f them w ere n o t i d e n t i f i e d a s to s p e c i e s , w h ile

o t h e r s w ere S ta p h y lo c o c c u s a u r e u s , S ta p h y lo c o c c u s a l b u s , a n d h e m o ly tic
s t a p h y l o c o c c i (1 9 ) .
S ta p h y lo c o c c u s p y o g e n e s was s u s p e c te d o f b e in g r e s p o n s i b l e f o r
g a s t r o i n t e s t i n a l d i s t u r b a n c e s i n a n o u tb r e a k ( 2 1 ) , w h ich r e s u l t e d from
i n g e s t i n g th e m e at o f a cow t h a t d i e d o f p u e r p e r a l f e v e r .
P r i o r to 1930 th e a b i l i t y o f s t a p h y l o c o c c i to e l a b o r a t e a s u b s ta n c e
c a p a b le o f p ro v o k in g symptoms o f f o o d p o is o n i n g i n human b e i n g was a lm o s t
u n s u s p e c te d .

The "m o d ern e r a " o f S ta p h y lo c o c c u s fo o d p o i s o n i n g , t h e r e ­

f o r e , d a t e s from 1 9 3 0 .

S in c e t h a t tim e o u r know ledge o f th e s u b j e c t h a s

i n c r e a s e d r a p i d l y , a n d t h i s m o st common o f a l l ty p e s o f f o o d p o is o n in g i s
now r e c o g n iz e d th r o u g h o u t th e c i v i l i z e d w o rld ( 1 8 ) .
W h ile t h e r e had b e e n i n d i c a t i o n s e a r l i e r t h a t t h e s e o rg a n is m s
m ig h t be a s s o c i a t e d w ith g a s t r o i n t e s t i n a l d i s t u r b a n c e s , i n g e n e r a l , t h e i r
p r e s e n c e i n s u s p e c te d f o o d s was a t t r i b u t e d to t h e i r u b i q u i t o u s n a t u r e .
Many f i l t r a t e s from e n t e r o t o x i g e n i c s t r a i n s o f s t a p h y l o c o c c i w ere
t r i e d on human v o l u n t e e r s an d t y p i c a l symptoms w ere p ro d u c e d (U 9 ,5 o ) .
Among f o o d s in v o lv e d i n S ta p h y lo co c c u s fo o d p o is o n in g l i s t e d by
H ay n es an d H u c k er (3 9 ) a r e v a r i o u s k in d s o f p i e and c a k e , u s u a l l y
c u s t a r d f i l l e d , i c e c re a m , b u t t e r , c h e e s e , e c l a i r s , cream p u f f s , b e e f ,
c h i c k e n , c h ic k e n g r a v y , c h ic k e n and ham p a s t e , c h ic k e n s a l a d , f r o z e n

9

p a c k v e g e t a b l e s , g ro u n d m e at s a n d w ic h e s , ham , h e a d c h e e s e s a n d w ic h e s ,
k i p p e r s , o y s t e r s , p a s t r y , p o t a t o s a l a d , s w e e t p o t a t o , c a n d y , an d to n g u e .
T hey l i s t th e f o o d s a f f e c t e d b y i n d i c a t i n g t h a t a lm o s t a n y a r t i c l e o f
f o o d w h ic h i s n o t p r o p e r l y p r e p a r e d an d r e f r i g e r a t e d may c a u s e f o o d
p o is o n in g o f t h i s t y p e .

D ack (1 6 ) n o te d t h a t s t a p h y l o c o c c i grow a b u n ­

d a n t l y i n c o n c e n t r a t i o n s o f s a l t a n d s u g a r , w h ic h k i l l o r p r e v e n t o t h e r
ty p e s fro m g ro w in g , s u c h a s i n c e r t a i n c u r e d m e a ts .

I n v e s t i g a t i o n s o n g ro w th o f S ta p h y lo c o c c u s i n fo o d s
F i t z g e r a l d ( 32 ) i n h i s r e p o r t on f r o z e n fo o d s n o te d t h a t th e y , h av e
b e e n r e m a r k a b ly f r e e fro m s u s p i c i o n o f b e in g h e a l t h h a z a r d s , b o th a s to
e n t e r o t o x i c fo o d p o is o n in g an d i n f e c t i o u s d i s e a s e s .

He w a rn ed t h a t

t h e r e i s a c o n s i d e r a b l e p o s s i b i l i t y t h a t p a th o g e n ic o rg a n is m s may s u r v iv e
t h e f r e e z i n g - s t o r a g e t r e a t m e n t an d r e t a i n s u f f i c i e n t v i a b i l i t y to c a u s e
in fe c tio u s d is e a s e s .

T h e re c o u ld be a s o u rc e o f i n f e c t i o n i n f r o z e n

f o o d s o f t h e v e r y b e s t q u a l i t y b e c a u s e th e s o u r i n g w ould n o t b e p r e s e n t
t o w arn t h e u s e r .

He s u g g e s te d c o n t r o l o n ly th r o u g h c a r e f u l s a n i t a t i o n

p ro c e d u re s i n f a c t o r i e s .

He a ls o m e n tio n e d t h a t l a b o r a t o r y m eth o d s o f

d e t e c t i n g t h e in c id e n c e o f t o x i g e n i c o r p a th o g e n ic s t r a i n s o f o rg a n is m s
a r e a t p r e s e n t in a d e q u a te and f r o z e n fo o d s may m o m e n ta rily b e i m p l i c a t e d
as h e a lth h a z a rd s.
J o n e s a n d L o ck h ead (h9) fo u n d t h a t o f th e £0 s t r a i n s o f s t a p h y l o ­
c o c c i fro m f r o z e n - p a c k v e g e t a b l e s , r e p r e s e n t i n g 980 i s o l a t i o n s , 12 s t r a i n s
w ere p o s i t i v e f o r e n t e r o t o x i n r e p r e s e n t i n g i i l l c u l t u r e s i s o l a t e d .

A ll th e

v e g e t a b l e p r o d u c ts t e s t e d by them w ere shown to h a r b o r one o r m ore s t r a i n s
c a p a b le o f e l a b o r a t i n g e n t e r o t o x i n when grown i n a s e m i - s o l i d medium i n

10

an a tm o s p h e re o f C 02 an d a i r and t e s t e d w ith t h e p i p e t t e - f e e d i n g m ethod
to k i t t e n s .
D a v id s o n an d D ack (2 0 ) n o te d t h a t c e r t a i n s t a p h y l o c o c c i c a n
e l a b o r a t e e n t e r o t o x i n i n e x p e r i m e n t a l l y i n o c u l a t e d c a n s o f c o r n and
o y s te rs .

T h is was d e m o n s tr a te d b y i n tr a v e n o u s i n j e c t i o n i n t o monkeys

an d f e e d i n g o f human v o l u n t e e r s .

H o w ev er, S ta p h y lo c o c c u s e n t e r o t o x i n was

n o t p ro d u c e d i n i n o c u l a t e d c a n n e d sa lm o n .
S e g a lo v e a n d Dack (7 9 ) fo u n d t h a t g ro w th o f s ta p h y l o c o c c i i n
c a n n e d fo o d s w as n o t n e c e s s a r i l y c o r r e l a t e d w ith e n t e r o t o x i n p r o d u c t i o n ,
an d one c a n c o n c lu d e t h a t i n t h e a b s e n c e o f g ro w th o f s t a p h y l o c o c c i no
e n te r o to x in i s p ro d u c e d .

T hey r e p o r t e d t h a t c a n n e d f o o d s o f lo w a c i d c o n ­

t e n t ( p e a s , c o r n ) ; s e m i - a c id c o n t e n t ( a s p a r a g u s , s p i n a c h , and s t r i n g
b e a n s ) ; m e d iu m -a c id c o n t e n t ( s a lm o n , sh rim p ) w e re e x p e r i m e n t a l l y in o c u ­
l a t e d w ith a fo o d p o is o n in g s t r a i n o f S ta p h y lo c o c c u s .a u r e u s .

Grow th th e n

was fo u n d to b e b e s t i n low a c i d f o o d s b u t n o t a f f e c t e d b y t h e k in d o f
fo o d .

I n h ig h a c i d f o o d s g ro w th d i d n o t o c c u r .

I n a lm o s t a l l c a s e s

g ro w th w as b e t t e r a t 22 C ( 7 1 .6 F ) th a n a t 37 C ( 9 8 .6 F ) .

The o rg a n is m

p ro d u c e d a c i d b u t no g a s i n th e c a r b o h y d r a t e s w h ich I t f e r m e n te d ; h ow ever
i n c a n n e d p e a s and c o r n g a s was p r o d u c e d .
C a t h c a r t an d Merz (6 ) r e p o r t e d t h a t n a t u r a l c h o c o la te ( f o u r o u n c e s )
and n a t u r a l c o c o a ( t h r e e o u n c e s ) f i l l i n g s made a c c o r d in g to a g iv e n fo rm u la
h a v e a d e f i n i t e i n h i b i t i n g a c t i o n o n th e g ro w th o f S ta p h y lo c o e c u s a u r e u s .
I t s e e m s , t h e r e f o r e , t h a t f i l l i n g s made w ith c h o c o la te and c o c o a ,a c c o r d in g
to t h e s p e c i f i e d fo rm u la w ith o u t an y e g g ,s h o u l d o f f e r l i t t l e
th e s t a n d p o i n t o f f o o d i l l n e s s c a u s e d b y S . a u r e u s ,

h a z a r d from

The pH o f th e f i l l i n g s

11

and a su b s ta n c e o r c o m b in a tio n o f s u b s ta n c e s i n c h o c o la t e and c o c o a are
r e s p o n s ib le fo r t h i s i n h i b i t i n g a c t i o n .

D ata in d ic a t e t h a t t h i s su b sta n c e

o r t h e s e s u b s ta n c e s are p r o b a b ly lo c a t e d i n th e n o n - f a t p a r t o f c h o c o la te
and c o c o a .
The a d d i t i o n o f c i t r i c a c i d to v a n i l l a f i l l i n g i n s u f f i c i e n t
am ounts to lo w e r th e pH to 3 .U3 to 3 .6 5 p ro v e d e f f e c t i v e i n c h e c k in g th e
g ro w th o f S . a u r e u s .

L a c t i c a c i d , when u s e d i n t h e p la c e o f c i t r i c a c i d ,

p ro d u c e d a b e t t e r t a s t i n g c h e e s e cak e f i l l i n g a n d e f f e c t i v e l y r e t a r d e d
t h e g ro w th o f S . a u r e u s a t pH v a lu e s b e tw ee n U.U2 a n d U .67 ( 6 ) .
S m ith and I b a (8 2 ) fo u n d t h a t when p i s t a c h i o n u t m e a ts w ere in o c u ­
l a t e d w ith S . a u r e u s t h e o rg a n is m s w o u ld i n c r e a s e i n number up t o a
maximum i n n in e d a y s a t room t e m p e r a t u r e .

The number o f v i a b l e S . a u r e u s

t h e n d e c r e a s e d u n t i l s t e r i l i t y o c c u r r e d i n 99 d a y s .

A t 9 8 .6 F th e m a x i­

mum c o u n t w as re a c h e d w i t h i n U8 h o u rs a f t e r w h ic h t h e r e was r a p i d d e s ­
tru c tio n .

V ia b le S . a u r e u s was n o t d e t e c t e d a f t e r 63 d a y s ,

M oorehead an d W e is e r ( 6i|.), a f t e r a s e r i e s o f e x p e r im e n ts , r e p o r t e d
t h e p o s s i b i l i t y t h a t s ta p h y l o c o c c i may b e commonly c a r r i e d b y f l i e s a s
w as e v id e n c e d b y t h e i s o l a t i o n o f s t a p h y l o c o c c i fro m th e d i g e s t i v e t r a c t
o f 10 o f t h e $0 w i l d f l i e s c a u g h t and e x a m in e d .

The h o u se f l y , Muse a

d o m e s t ic a , may s e r v e a s a r e s e r v o i r h o s t f c r S . a u r e u s , a n d i t i s
p o s s i b l e t h a t u n d e r s u i t a b l e c o n d i t i o n s th e f l y may i n i t i a t e o r augm ent
a f o o d p o is o n in g o u tb r e a k b y s p r e a d in g s ta p h y l o c o c c i fro m i n f e c t e d
h a n d l e r s o r d i r t y e q u ip m e n t to f o o d , an d from c o n ta m in a te d s u p p l i e s to
good f o o d s t u f f s w h ic h a r e f a v o r a b l e f o r e n t e r o t o x i n p r o d u c t i o n .

12

E n te ro to x in p ro d u c tio n by s ta p h y lo c o c c i
A lth o u g h B a r b e r ( l )

e s t a b l i s h e d th e r e l a t i o n s h i p b e tw e e n t h e

s t a p h y l o c o c c i i s o l a t e d and t h e symptoms n o te d i n an o u tb r e a k th r o u g h
human e x p e r i m e n t a t i o n , th e w ork was n o t w e l l known u n t i l 1930 when Dack
e t a l ( 1 3 ) c o n f ir m e d and a u g m en ted h i s r e s u l t s .
The u s e o f human v o l u n t e e r s h a s b e e n l a r g e l y d i s c o n t i n u e d , b u t
s i n c e no l a b o r a t o r y a n im a l seem s t o be a s s u s c e p t i b l e a s man w hen f e d
p o t e n t f i l t r a t e s , r e s o r t t o human v o l u n t e e r s i s a d v i s a b l e w h e n ev e r i n ­
c o n c lu s iv e r e s u l t s a r e o b t a i n e d ( 19 ) .
Dolman (2 7 ) w ro te t h a t i t h a s b e e n a c c e p te d t h a t t h e a c t i o n o f
th e e n t e r o t o x i n i s n o t d i r e c t l y u pon t h e g a s t r o i n t e s t i n a l t r a c t , b u t
r a t h e r u p o n some s p e c i f i c a r e a o f th e c e n t r a l n e rv o u s s y s te m .

The n a t u r e

o f t h e s t im u lu s and t h e e x a c t l o c a t i o n o f t h e s u s c e p t i b l e a r e a a r e u n ­
known.

H ow ever, B a y l i s s ( 2 ) p r e s e n t e d im p o r ta n t e v id e n c e a s t o th e

p r o b a b le p a th w a y s o f th e r e f l e x a n d t h e l o c a t i o n o f th e c e n t e r , in v o lv e d
i n th e f e l i n e v o m itin g r e a c t i o n in d u c e d b y e n t e r o t o x i n .
W o o lp e r t an d Dack (9 9 ) p ro d u c e d symptoms s i m i l a r to th o s e i n man
i n R h esu s m onkeys w ith p r e p a r e d t o x i n .

They c o n c lu d e d t h a t m onkeys a r e

u s e f u l i n d e t e c t i n g th e t o x i n i n l a r g e a m o u n ts.

D ack (1 9 ) f e d s i x m onkeys

w i t h v e a l i n f u s i o n b r o t h f i l t r a t e o f t h e o rg an ism ., a n d , i f one v o m ite d i t
w as c o n s id e r e d p o s i t i v e e v id e n c e o f e n t e r o t o x i n .

When th e f i l t r a t e was

t r e a t e d w ith e t h a n o l , a l a r g e am ount was r e q u i r e d to e l i c i t th e sym ptom s.
T h e re was a l s o some e v id e n c e t h a t t r y p s i n d e s tr o y e d th e e n t e r o t o x i n ,
w h ic h was p ro d u c e d b e s t i n s e m i s o l id v e a l i n f u s i o n a g a r i n t h e a tm o sp h e re
o f 8 -2 0 p e r c e n t C 02 .

13

Dolman (2 3 ) p ro v e d t h e e v i d e n t f a i l u r e o f f o r m a l i n i z a t i o n to
d e t o x i c a t e t h e e n t e r o t o x i c com ponent o f c e r t a i n f i l t r a t e s w i t h i n th e
tim e w h ic h s u f f i c e s to r e n d e r a l l th e h e m o l y t i c , n e c r o t i z i n g , and a c u t e l y
l e t h a l s u b s ta n c e s c o n ta i n e d t h e r e i n .

T h is f a c t m akes i t m o st d e s i r a b l e

t h a t no e n t e r o t o x i g e n i c s t r a i n o f s t a p h y l o c o c c i s h o u ld b e u s e d i n t h e
p r o d u c t i o n o f S ta p h y lo c o c c u s t o x o i d f o r a c t i v e im m u n iz a tio n o f human
b e in g s .
H o p k in s a n d P o la n d ( h i ) c o n c lu d e d fro m t h e i r e x p e r im e n t t h a t i n t r a p e r i t o n e a l i n j e c t i o n s i n t o s u c k l i n g p i g s o f S ta p h y lo c o c c u s f i l t r a t e s
c o n t a i n i n g e n t e r o t o x i n c o u ld in d u c e v o m itin g , a s o b s e r v e d i n 53 o f 57
p ig s t e s t e d .

The s p e c i f i c i t y o f t h i s r e s p o n s e was i n d i c a t e d to them b y

f a i l u r e o f t h e a n im a ls to r e a c t when i n j e c t e d w ith a u to c l a v e d f i l t r a t e s
fro m e n t e r o t o x i c s t r a i n s , f i l t r a t e s fro m n o n e n t e r o to x ic s t r a i n s , o r f i l t e r ­
ed u n i n o c u l a t e d m edium .

I n c o n t r a s t w ith o t h e r a n im a ls u s e d f o r e n t e r o ­

t o x i n t e s t s , young p i g s a r e c h e a p an d o b t a i n a b l e an y tim e o f th e y e a r .
V ery l i t t l e

s p e c i a l a t t e n t i o n i s r e q u i r e d b y th e a n im a l

o th e r th a n fe e d ­

i n g a c o m p le te d r y r a t i o n o n ce a d ay and s u p p ly in g i t w i t h w a t e r .
Dack (1 9 ) s t a t e d t h a t e n t e r o t o x in i s r e l a t i v e l y h e a t s t a b l e i n a
cru de form and i t s c h e m ic a l n a tu re d i f f i c u l t to d e te r m in e .
L

The g r e a t m a j o r i t y o f p a th o g e n ic human s t r a i n s o f s t a p h y l o c o c c i
a re d e f i n i t e l y to x ig e n ic under a p p ro p ria te i n v itr o c o n d itio n s o f
g ro w th .

O th e r t o x i g e n i c s t r a i n s may b e i s o l a t e d fro m human s t a p h y l o ­

coccal in fe c tio n s .

S t r a i n s o f s t a p h y l o c o c c i o b t a in e d fro m a p p a r e n t l y

h e a l t h y m ucous m em branes o f t h e n o se and t h r o a t may p ro v e e x tr e m e ly t o x i ­
g e n ic w hen grow n i n v i t r o

( 2 ii) .

Ik

I f a f o o d c o n ta m in a te d w ith e n t e r o t o x i g e n i c s t a p h y l o c o c c i be
p l a c e d i n t e r m i t t e n t l y i n t h e r e f r i g e r a t o r , an d t h e r e s t o f t h e tim e e x ­
p o s e d to warm t e m p e r a t u r e s , t h e o rg a n is m s may e l a b o r a t e s u f f i c i e n t e n t e r o ­
t o x i n t o r e n d e r t h e fo o d p o is o n o u s .

E ven a t th e a v e r a g e te m p e r a tu r e o f

a warm room 2 0 -2 3 C, ( 6 8 - 7 3 . h F ) , e n t e r o t o x i n p r o d u c t i o n c a n i n a s h o r t
p e r i o d r e a c h a l e v e l o f p o te n c y s u f f i c i e n t t o c a u s e p o i s o n i n g i n m an.
S e g a lo v e and D ack ( 7 8 ) , u s in g a s u i t a b l e s t r a i n o f f o o d p o is o n in g
S ta p h y lo c o c c u s , fo u n d t h a t e n t e r o t o x i n c o u ld b e d e m o n s tr a te d i n a c u l t u r e
grow n f o r t h r e e d a y s a t 18 C an d f o r 12 h o u rs a t 37 C .

I t was n o t p r o ­

d u c e d i n c u l t u r e s grown f o r s h o r t e r p e r i o d s a t t h e s e t e m p e r a t u r e s .

At

9 C and 15 C (5 9 F ) i t w as n o t p ro d u c e d i n s e v e n and t h r e e d a y s , r e s p e c ­
tiv e ly .

A t h to 6 ,7 C e n t e r o t o x i n was n o t fo rm ed a f t e r a p e r i o d o f f o u r

w eek s o f i n c u b a t i o n .
The e n t e r o t o x i g e n i c i t y o f s t r a i n s i s o f t e n l o s t o r g r e a t l y l e s s e n e d
b y g ro w th o n a r t i f i c i a l m e d ia .

J o r d o n and B u rro w s (5 3 ) fo u n d t h a t g ro w th

u n d e r C 0 2 r e a c t i v a t e d c e r t a i n s t r a i n s , w h ile c e r t a i n o t h e r s , n o t known to
p ro d u c e e n te r o to x in ,b e c a m e a c t i v e .

Symptoms
Dolman (2 7 ) n o te d t h a t th e sym ptom ology i n a n a c u te o u tb r e a k o f
S ta p h y lo c o c c u s f o o d p o is o n in g i s so c h a r a c t e r i s t i c t h a t d i a g n o s i s seld o m
n e e d s b e i n d o u b t.

A f t e r a sy m p to m less i n t e r v a l o f u s u a l l y 1 —1+ h o u rs

f o llo w e d b y a p e r i o d o f n a u s e a w h ich may l a s t from o n ly a few m in u te s up
t o n e a r l y a n h o u r , su d d en v o m itin g o c c u r s .

S e v e r a l b o u ts o f v o m itin g

may e n su e o v e r th e n e x t few h o u r s , and t h e r e may a l s o b e a b d o m in a l cram ps

15

a n d m a rk e d d i a r r h e a .

The p u l s e i s r a p i d a n d i n s e v e r e e a s e s may become

t h r e a d y , t h e te m p e r a tu r e i s o f t e n r a i s e d an d th e p a t i e n t may b e c o l l a p s e d
a n d a p p r e h e n s iv e w ith num bness o f t h e e x t r e m i t i e s , p a l l o r an d c o l d s w e a ts .
A f t e r 3-U h o u r s , an d so m etim es e a r l i e r , im p ro v em en t s e t s i n , c o l o r r e ­
t u r n s , th e p u l s e becom es s t r o n g e r , an d a d e s i r e f o r fo o d a n d d r i n k may b e
e x p re sse d .

O f t e n , h o w e v e r, f o r a d a y o r two an d so m etim es l o n g e r , a n o r e x ia

may p e r s i s t , w i t h n a u s e a , d i a r r h e a o r a b d o m in a l d is c o m f o r t a n d c o n s i d e r ­
a b le l o s s i n w e i g h t .

The m o r t a l i t y r a t e fro m S ta p h y lo c o c c u s f o o d p o is o n ­

i n g i s c e r t a i n l y v e r y lo w , b u t a few a p p a r e n t l y a u t h e n t i c f a t a l i t i e s a r e
on r e c o r d .

Kodama, H a t a , an d S ib u y a (5 5 ) r e p o r t e d a p re m a tu re b i r t h , w ith

d e a t h o f th e i n f a n t , f o l l o w i n g a n a t t a c k due t o f i s h s a u s a g e .
O v e rg ro w th o f f o o d p o is o n in g s ta p h y l o c o c c i
by o th e r b a c te r ia in fo o d s tu ff s
C o u n ts o f from 1 0 0 ,0 0 0 to 1 m i l l i o n s t a p h y l o c o c c i p e r gram o f fo o d
m a t e r i a l a r e u s u a l , a c c o r d in g t o D olm an (2 7 ) .

Such low c o u n ts c a n o n ly

be r e c o n c i l e d w ith e n t e r o t o x i c p r o p e r t i e s i n a g iv e n fo o d b y s u p p o s in g
t h a t a m ark ed d e c l i n e i n b a c t e r i a l p o p u l a t i o n o c c u r s a f t e r a n e a r l y p h a se
o f r a p i d p r o l i f e r a t i o n w ith m axim al e n t e r o t o x i n p r o d u c t i o n .

When a ra m p a n t

P r o t e u s s t r a i n i s th e c o m p e tin g o rg a n is m , i t may b e im p o s s ib le t o d e t e c t
a n y s t a p h y l o c o c c i i n th e fo o d s t u f f b y t h e o r d i n a r y m eth o d o f c u l t u r e o n
b lo o d a g a r p l a t e s .
I f a h ig h d i l u t i o n o f th e s u s p e n s io n i s u s e d , s t a p h y l o c o c c i may
s u f f i c i e n t l y o u tn u m b er t h e P r o t e u s to grow w ith o u t h i n d r a n c e .

In fo o d ­

s t u f f s o f lo n g k e e p in g q u a l i t i e s no s ta p h y l o c o c c a l c o l o n i e s an d o n l y a
few c o l o n i e s o f P r o t e u s o r o t h e r o rg a n is m s may b e i s o l a t e d .

16
T h is f i n d i n g may b e a n e x p l a n a t i o n o f th o s e s a l m o n e l l o s i s o u t ­
b r e a k s , i n w h ic h o c c a s i o n a l c a s e s m a n i f e s t a b r i e f i n c u b a t i o n p e r i o d a s
i n th e r e p o r t o f H in d e n ( h i ) , t he e a r l y o n s e t b e in g due to p re fo rm e d
S ta p h y lo c o c c u s e n t e r o t o x i n .

A c tio n o f c h e m ic a l a g e n ts u pon e n t e r o t o x i n
H aynes a n d H u c k e r (3 9 ) r e p o r t e d t h a t t h e a c t i o n o f c h e m ic a l a g e n ts
u p o n e n t e r o t o x i n i s a s u b j e c t w h ic h h a s f o r t h e m o st p a r t b e e n n e g l e c t e d .
F r a g m e n ta ry r e p o r t s i n th e l i t e r a t u r e seem to i n d i c a t e t h a t th e e n t e r o ­
t o x i n i s a c o n ju g a te p r o t e i n o f t h e l i p o p r o t e i n t y p e .
i s in d ic a te d by i t s

e th e r s o l u b i l i t y .

I t s l i p o i d a l n a tu re

I t s i n s o l u b i l i t y in s a tu r a te d s o lu ­

t i o n s o f ammonium s u l f a t e , a s shown by D a v is o n and D ack ( 2 0 ) , a n d i t s
s u s c e p t i b i l i t y to t r y p s i n (6 2 ) a r e i n d i c a t i o n s o f i t s p r o t e i n n a t u r e .
I t s t o x i c i t y i s n o t a l t e r e d by a c t i o n o f c h l o r i n e (lU ) an d a c i d (pH 3 .0 )
o r r e n n e t a s shown b y M in n e tt ( 62 ) .
E f f e c t o f p h y s i c a l a g e n ts upon e n t e r o t o x i n
The m o st p ro m in e n t p h y s i c a l p r o p e r t y o f e n t e r o t o x i n i s i t s h e a t
s ta b ility .

T h e re h a s b e e n much c o n t r o v e r s y on t h i s p o i n t .

D a v iso n and

D ack (2 0 ) c o n firm e d th e i n s t a b i l i t y o f e n t e r o t o x i n u n d e r p r o lo n g e d h e a t ­
i n g , a n d th e y fo u n d t h a t a u t o c l a v i n g d e c r e a s e d i t s p o te n c y .
J o n e s and L o ck h ead (U9) r e p o r t e d t h a t e n t e r o t o x i n , b e s i d e s d i f f e r ­
in g fro m o r d i n a r y e x o to x in i n i t s r e s i s t a n c e to h e a t i n g , r e t a i n e d i t s
t o x i c i t y when s t o r e d a t low te m p e r a t u r e s f o r two m o n th s .

A lth o u g h i t

d i f f u s e s f r e e l y i n t o th e c u l t u r e m edium , e n t e r o t o x i n d i f f u s e s o n ly

17

s l i g h t l y th r o u g h c o l l o d i o n (6 2 ) .

I t i s p a r t i a l l y a b s o r b e d on S e i t z p a d s

d u r in g f i l t r a t i o n b u t to a l e s s e r e x t e n t t h a n o t h e r t o x i c f a c t o r s p r e s e n t
i n S ta p h y lo c o c c u s f i l t r a t e s .

J o rd o n an d B u rro w s (5 0 ) fo u n d t h a t e n t e r o ­

t o x i n w ou ld n o t d i s t i l l .

A n tig e n ic ity o f e n te ro to x in
Dolman an d W ils o n ( 2 5 , 26) an d M i n e t t (6 2 ) c o n firm e d t h e demon­
s t r a t i o n o f th e a n t i g e n i c i t y o f e n t e r o t o x i n .

The f i r s t two w ere f u r t h e r

a b le to d e m o n s tr a te a f l o c c u l a t i o n r e a c t i o n i n v o l v i n g t h e e n t e r o t o x i n
and t h e s p e c i f i c a n t i b o d y .
D a v iso n and D ack (2 0 ) m ixed a n e n t e r o t o x i c s t a p h y l o c o c c a l f i l t r a t e
w i t h an e q u a l am ount o f m onkey a n tis e r u m p r e p a r e d a g a i n s t a n o n fo o d p o is o n ­
in g S ta p h y lo c o c c u s .

The s m a l l e s t am ount o f t h i s t r e a t e d f i l t r a t e

th a t

w o u ld g iv e c o n s i s t e n t p o s i t i v e r e s u l t s o f p o is o n in g symptoms when i n ­
j e c t e d i n t r a v e n o u s l y i n t o m onkeys was 0 . 1 to 0 .2 c c . p e r k i l o b o d y w e ig h t.
Dack (1 5 ) fou n d t h a t o r a l a d m in is tr a tio n o f p o te n t f i l t r a t e s to
man and r a b b it s was i n e f f e c t i v e i n s t im u la t in g th e p r o d u c tio n i n them o f
a n t ib o d ie s a g a in s t th e e n t e r o t o x in .

A p p a r e n tly some d eg ree o f imm unity

may be d e v e lo p e d i n in d iv id u a ls by o r a l a d m in is tr a tio n o f e n te r o to x in ,,
b u t c o n s i s t e n t r e s u l t s a r e o n ly o b ta in e d by p a r e n te r a l a d m in is t r a t io n .
The c o n t r o l o f S ta p h y lo c o c c u s fo o d p o is o n in g
H ussem an and T a n n e r (U5) p o i n t e d o u t t h a t e v e r y e m p h a sis m u st be
g iv e n to th e f a c t t h a t i n c a s e o f S ta p h y lo c o c c u s fo o d p o is o n i n g th e
d a n g e r i s n o t a l l e v i a t e d e i t h e r by c h i l l i n g , o r i n some c a s e s , b y h e a t i n g

16

t h e fo o d o n ce i t h a s b e e n a llo w e d to s t a n d a t room t e m p e r a t u r e .

N e ith e r

c o l d n o r h e a t i n g to t h e b o i l i n g p o i n t f o r one h a l f h o u r o r m ore d e s t r o y s
t h e t o x i n o n c e i t h a s b e e n fo rm e d .

Once t h e t o x i n i s fo rm ed t h e r e i s

a p p a r e n t l y no r e l i a b l e way o f f r e e i n g t h e fo o d o f i t .
They a l s o r e p o r t e d t h a t i n an e x a m in a tio n o f a l a r g e num ber o f
d i f f e r e n t p r e p a r e d f o o d s , a t l e a s t 20 p e r c e n t s e r v e d i n p u b l i c p l a c e s
w ere i n f e c t e d w i t h s t a p h y l o c o c c i .

T h ese f o o d s , a p p a r e n t l y p r o p e r l y h a n d le d ,

d id n o t so f a r a s was known c a u s e i l l n e s s .

I t i s n o t known w i t h c e r t a i n t y

w h e th e r a l l s t a p h y l o c o c c i a r e p o t e n t i a l e n t e r o t o x i n f o r m e r s , g iv e n th e
p r o p e r e n v ir o n m e n ts .

I t i s m ore l i k e l y t h a t o n ly c e r t a i n s t r a i n s o f s t a p h y l o ­

c o c c i p ro d u c e e n t e r o t o x i n , b u t a s y e t t h e r e i s no way o f s e g r e g a t i n g t h e s e
s tra in s .
S to n e (8 8 ) c la im e d t h a t f a i l u r e to c o o l m ilk p r o m p tly , o r t o m a in ­
t a i n i t and o t h e r i n g r e d i e n t s o f d a i r y p r o d u c ts a t a low te m p e r a tu r e i s
m a in ly r e s p o n s i b l e f o r good p o is o n in g o u tb r e a k s c a u s e d b y s t a p h y l o c o c c i i n m i l k .
Dack (1 7 ) i n h i s d i s c u s s i o n on b a c t e r i a l f o o d p o is o n i n g s an d t h e i r
im p o r ta n c e i n th e b a k in g i n d u s t r y p o i n t e d to r e f r i g e r a t i o n a s th e m o st
e f f i c i e n t p re v e n tiv e .

F o r cream p u f f s , r e h e a t i n g a f t e r f i l l i n g fo llo w e d

b y r e f r i g e r a t i o n seem s m o st e f f e c t i v e .
M ore and m ore e v id e n c e a c c u m u la te s to s u g g e s t t h a t th e human e le m e n t,
t h e fo o d h a n d l e r s , may be t h e r e a l s o u rc e o f e n t e r o t o x i n fo rm in g s t a p l y l o c o c c i e s p e c i a l l y i n b a k e r i e s ( 67 ) .

P e rs o n s w i th c o l d s , w ith s u p p u r a tin g

l e s i o n s on h a n d s , arm s o r f a c e , o r w ith d i a r r h e a s h o u ld b e rem oved from
f o o d p r e p a r a t i o n and s e r v i c e a c t i v i t i e s .

T a y lo r (9 0 ) a d v o c a te d t h a t

fo o d h a n d l e r s be rem oved from, t h e i r w ork when fo u n d by m e d ic a l e x a m in a ­
t i o n to b e a p o s s i b l e s o u rc e o f c o n ta m in a tio n w ith S t a p h y lo c o c c u s ,

19

t h a t f o o d b e n o t l e f t a t room te m p e r a t u r e m ore t h a n f o u r h o u r s , an d t h a t
t h e r e b e th o r o u g h c o o k in g b e f o r e s e r v i n g l e f t o v e r f o o d .
J e n s e n (2+7) a l s o e m p h a s iz e d th e im p o r ta n c e o f n o t k e e p in g fo o d f o r
any l e n g t h o f tim e i n t h e i n c u b a t i o n d a n g e r z o n e , w h ic h he gave a s fro m
5 0 -1 2 0 F .

The d a n g e r tim e w i t h i n t h i s z o n e '"is li-8 h o u r s d e p e n d in g on th e

e x t e n t to w h ic h t h e fo o d i s s u i t a b l e f o r b a c t e r i a l g ro w th .
s l i c e d and s e rv e d a t o n c e .
tu rk e y o r o th e r fo w ls .

Ham s h o u ld be

The same p r o c e d u r e s h o u ld b e f o llo w e d w i t h

The s t u f f i n g o r d r e s s i n g m u st n o t b e h e ld a t

te m p e r a t u r e s ab o v e 50 o r b e lo w 130 F f o r a l o n g e r p e r i o d th a n f o u r h o u r s .
D e h y d ra te d fo o d s do n o t u n d e rg o b a c t e r i a l s p o i l a g e i f t h e m o is tu r e c o n ­
t e n t i s b e lo w 10 p e r c e n t .

They s h o u ld n o t b e h e ld i n t h e te m p e r a tu r e

i n c u b a t i o n zone l o n g e r t h a n 3 h o u rs a f t e r t h e w a te r i s a d d ed b e f o r e th e y
a r e co n su m ed .
Dack (1 7 ) sum m arized th e s e v e r a l c o n d i t i o n s n e c e s s a r y f o r S ta p h y lo ­
c o c c u s fo o d p o is o n in g to o c c u r a s f o l l o w s :
1 . Food m u st b e c o n ta m in a te d w ith a s t r a i n o f t o x i n fo rm in g
S ta p h y lo c o c c u s s in c e many s t r a i n s do n o t p ro d u c e t h e t o x i n .
2 . F ood m u st c o n t a i n t h e p r o p e r n u t r i t i v e r e q u ir e m e n ts i n c l u d ­
i n g s u c h f a v o r a b l e c o n d i t i o n s a s t h e p r o p e r am ount o f
m o is tu r e and d e g re e o f a c i d i t y o r a l k a l i n i t y .
3 . S u i t a b l e te m p e r a tu r e f o r g ro w th o f s ta p h y l o c o c c i i n f o o d .

hm S u f f i c i e n t tim e i n t e r v a l f o r g ro w th and t o x i n f o r m a t i o n .
He p o i n t e d o u t t h a t s ta p h y l o c o c c i a l o n e , w ith o u t t h e i r g ro w th
p r o d u c t s c a u s e no i l l e f f e c t s when f e d to man.

A t p r e s e n t a d e q u a te

r e f r i g e r a t i o n o f p e r i s h a b l e fo o d i s t h e o n ly s a f e g u a r d a g a i n s t S ta p h y lo ­
co ccu s fo o d p o is o n in g .

20

I n t h e f i e l d o f e d u c a tin g fo o d h a n d l e r s g r e a t s t r i d e s have b e e n
m ad e.

D odson (2 2 ) , M o rg a n , M u se, a n d M c K e lla r (6 5 ) p r e p a r e d s h o r t

c o u r s e s f o r fo o d h a n d l e r s i n w h ich t h e n e c e s s a r y p r e c a u t i o n s a r e o u t l i n e d .
W ith th e a f o r e m e n tio n e d c h a r a c t e r i s t i c s and g ro w th r e q u ir e m e n ts
o f f o o d p o is o n in g s t a p h y l o c o c c i i n m in d , i t i s th e p u rp o s e o f t h i s i n ­
v e s t i g a t i o n to f i n d a way to i n h i b i t them, o n m e a ts b y th e u s e o f a ch em i­
c a l a g e n t w here a d e q u a te r e f r i g e r a t i o n i s n o t a v a i l a b l e .

21

S a lm o n e lla food, p o is o n i n g

Im p o rta n c e
As D olm an ( 27 ) p o i n t e d o u t t h a t fo o d p o is o n in g o u tb r e a k s a r e
n o to rio u s f o r u n r e l i a b i l i t y o f s t a t i s t i c s r e s p e c tin g t h e i r in c id e n c e .
T h e re i s some r e a s o n to b e l i e v e t h a t S a lm o n e lla f o o d p o is o n in g may b e
r e l a t i v e l y m ore p r e v a l e n t i n B r i t a i n th a n i n N o rth A m e ric a .
The f i r s t o u tb r e a k o f S a lm o n e lla f o o d p o is o n in g due to i n g e s t i o n
o f t h e m e a t o f a cow i n S a x o n y , G erm any, i n 1888 w as c a u s e d by S a lm o n e lla
e n te ritid is .

T he cow had b e e n d i s e a s e d (1 8 ) .

A c c o rd in g to H in d e n (1+1) i n E n g la n d an d W ales 299 o u tb r e a k s o f
S a lm o n e lla fo o d p o is o n in g w ere r e p o r t e d from 1 9 2 3 -3 7 9 a f f e c t i n g 1+1+18
p e r s o n s o f whom. 102 d i e d .

I n 1937 a lo n e 1+5 o u t b r e a k s i n t h e U n ite d S t a t e s

w e re r e p o r t e d in v o l v i n g 601 c a s e s an d 21+ d e a t h s ,

F u c h s (3 3 ) r e p o r t e d

f o r t h e U n ite d S t a t e s i n 1939, ll+8 o u tb r e a k s o f a l l . k in d s in v o l v i n g 3782
c a s e s w ith 12 d e a t h s , g i v i n g a r e l a t i v e l y low i n c id e n c e o f S a lm o n e lla f o o d
p o is o n in g .

As w i l l be shown l a t e r S a lm o n e lla e do n o t '•p o iso n " f o o d , a n d

t h e te rm S a lm o n e lla fo o d i n f e c t i o n h a s come to h a v e m ore m e an in g s in c e
t h i s i n f e c t i o n o f fo o d p o is o n in g ty p e i s c a u s e d b y a g r e a t num ber o f
o r g a n is m s .

The r o l e o f S a lm o n e lla fo o d i n f e c t i o n i n d e h y d r a te d fo o d s

w i l l be d i s c u s s e d .

The p o s s i b i l i t y t h a t s a lm o n e lla e may re m a in a l i v e and

v i r u l a n t i n d e h y d r a te d fo o d s h a s a d d e d m ore im p o r ta n c e to t h i s ty p e o f
o u tb re a k .
I n g e n e r a l , S a lm o n e lla c a u s e two ty p e s o f i n f e c t i o n ( 1 8 ) .

One

group a p p a r e n t l y p a r a s i t i z e s o n l y man an d p ro d u c e s a n i n f e c t i o n an d

22

sym ptom s s i m i l a r t o , b u t m i l d e r t h a n , ty p h o id f e v e r .
b e lo n g th e s p e c i e s S . p a r a t y p h i a n d
c a r r i e r o f t h e s e o r g a n is m s .

s c h o ttm u lle ri.

To t h i s g ro u p
Man may becom e a

The s e c o n d g ro u p p r o d u c e s i n a n im a ls a

d i s e a s e s i m i l a r to ty p h o i d f e v e r i n m an, a n d i f i n g e s t e d i n l a r g e num bers
b y man p ro d u c e s one o r m ore o f th e f o l l o w i n g sym ptom s:
a b d o m in a l c r a m p in g , an d d i a r r h e a .
a ls o p r e s e n t.

n a u s e a , v o m itin g ,

F r e q u e n t l y f e v e r an d l e u k o c y t o s i s a r e

S . e n t e r i t i d i s i s t h e i m p o r ta n t o rg a n is m i n t h i s g ro u p .

I n d i v i d u a l s r e c e i v i n g a s m a l l d o se o f t h e o rg a n is m s may e s c a p e w i th o u t
sym ptom s, and n o t a l l i n d i v i d u a l s r e a c t s i m i l a r l y .
Some o u tb r e a k s o f S a lm o n e lla fo o d i n f e c t i o n
W h ile t h e l i t e r a t u r e i s f u l l o f r e p o r t s , a l i m i t e d num ber o f o u t ­
b r e a k s i s m e n tio n e d h e r e a s r e p r e s e n t a t i v e o f t h i s w id e s p r e a d i n f e c t i o n .
D r o b i n s k i i an d Zmew (2 8 ) r e p o r t e d a num ber o f c a s e s o f f o o d p o i s o n ­
i n g b y m e a t w here t h e t o x i c e f f e c t s w ere m o st p r o b a b l y c a u s e d by th e
G a e r tn e r b a c i l l u s i n E u r o p e .

J u d e f i n d (51;) r e p o r t e d a r e l a t i v e l y s e v e r e

an d p r o t r a c t e d d i a r r h e a p re s u m e d ly due to S a lm o n e lla p u llo r u m from t h e
i n g e s t i o n o f in c o m p le te l y co o k ed e g g s .

I n C h i l e i n 19U? O r t i z a r ( 69 )

n o te d a n o u tb r e a k o f f o o d p o is o n in g i n 130 p e r s o n s i n an e d u c a t i o n a l
I n s t i t u t e i n S a n tia g o .

The i n c u b a t i o n p e r i o d o f 12-21; h o u r s , th e su d d e n

o n s e t , a n d t h e symptoms o f n a u s e a , v o m itin g , a b d o m in a l p a i n , and d i a r r h e a
w ere n o t e d .

The a t t a c k o f t e n b eg an w ith h e a d a c h e an d c h i l l s .

i n t e n s e f e v e r , t h i r s t , a n d m u s c u la r d i s a b i l i t y .
i d e n t i f i e d a s S a lm o n e lla ty p h im u riu m .

T h e re w ere

The c a u s a l o rg a n ism was

23

S a lm o n e lla d u b l i n w as known t o c a u s e a n o u tb r e a k o f fo o d p o is o n in g
due t o c o n ta m in a te d m ilk ( 5 l ) .
S a lm o n e lla p u llo r u m and S . p a r a t y p h i B ( S . s c h o t t m u l l e r i ) h a v e
b e e n i s o l a t e d fro m h e n e g g s ( 5 ) .

M itc h e l e t a L ( 63 ) r e p o r t t h a t i n ­

v e s t i g a t i o n o f a n e x p l o s i v e o u tb r e a k o f g a s t r o e n t e r i t i s , i n v o l v i n g a
known t o t a l o f a t l e a s t I4.23 i n d i v i d u a l s , i n d i c a t e d t h a t t h e o u tb r e a k
c o u ld be t r a c e d to t h e i n g e s t i o n o f a r i c e c u s t a r d p r e p a r e d fro m u n co o k ed
eg g s.

T he sym ptom s w e re s e v e r e e n o u g h to r e q u i r e h o s p i t a l i z a t i o n o f 172

o f th e a f f e c te d in d iv id u a ls .

S . p u llo r u m was i s o l a t e d fro m t h e s t o o l s

o f a s i g n i f i c a n t num ber o f p a t i e n t s i n s p i t e o f s u lfo n a m id e t r e a t m e n t .
T h i s o rg a n is m w as b e l i e v e d t o b e t h e c a u s e o f t h e e p id e m ic an d w as c o n ­
s i d e r e d to h a v e b e e n i n t r o d u c e d i n t o t h e r i c e c u s t a r d i n e g g s o b ta i n e d
fro m i n f e c t e d f o w l .

S . p u llo r u m i s u s u a l l y c o n s i d e r e d to b e n o n - p a t ho g e n ic

f o r humans a lth o u g h o c c a s i o n a l r e p o r t s h ave i n d i c a t e d i t s i s o l a t i o n fro m
s t o o l s o f a few s p o r a d ic c a s e s o f g a s t r o e n t e r i t i s .

I n v ie w o f t h e common

o c c u r r e n c e o f t h i s o rg a n is m i n e g g s w h ic h p l a y s u c h a n i m p o r ta n t r o l e i n
human d i e t , t h e r o l e o f S . p u llo r u m a s a human p a th o g e n m u st b e r e a s s e s s e d .
T u c k e r e t a l . (9 1 ) r e p o r t e d t h a t a n e p id e m ic w as t r a c e d to C o lb y
c h e e s e fro m w h ich S . ty p h im u riu m w as i s o l a t e d w ith o u t d i f f i c u l t y .

E x p e ri­

m e n ta lly i t was fo u n d t h a t t h e o rg a n is m w as v i a b l e f o r 362 d a y s i n c h e e s e
s t o r e d a t I43-U 8 F .

R eau d (7 1 ) d e s c r i b e d a n o u tb r e a k o f g a s t r o e n t e r i t i s

c a u s e d b y S . ty p h im u riu m .

The g e n e r a l sym ptoms i n c lu d e d v o m itin g ,

d i a r r h e a , a b d o m in a l p a i n , f e v e r , and p r o s t r a t i o n .

The i n i t i a l e p id e m io ­

l o g i c a l i n v e s t i g a t i o n in v o lv e d a c o n s i d e r a t i o n o f th e e p id e m ic a s a f o o d b o rn e d i s e a s e .

C l i n i c a l e x a m in a tio n o f t h e fo o d h a n d l e r s i n th e

i n s t i t u t i o n and a c u r s o r y e x a m in a tio n o f t h e fo o d consum ed b y t h e p a t i e n t s

2k

f a i l e d to r e v e a l th e s o u r c e o f t h e i n f e c t i n g o r g a n is m s .

The e p id e m io ­

l o g i c a l e v id e n c e o b t a i n e d i n d i c a t e d t h a t t h e d r i n k i n g w a te r w as c o n ­
t a m in a te d b y r a t s w h ic h w ere b e l i e v e d t o be t h e o r i g i n o f t h e o u tb r e a k o f
th e d is e a s e .

G r e e n b l a t t e t a l . (3 7 ) r e p o r t e d a f o o d p o i s o n i n g o u tb r e a k

i n v o l v i n g 97 tfien o v e r a f o u r d ay p e r i o d a t a n arm y cam p.

C o m m e rc ia lly

p r e p a r e d s a n d w ic h e s , a l l o f w h ic h c o n t a i n e d a home made m a y o n n a is e , w ere
a p p a re n tly r e s p o n s ib le .

S . ty p h im u riu m w as t h e e t i o l o g i c a l a g e n t .

The

s o u r c e o f t h e i n f e c t i o n was n o t d e te r m in e d .
U s in g 36 d i f f e r e n t b a c t e r i o p h a g e s , L ilh e e n g e n (5 8 ) h a s e n d e a v o u re d
t o c l a s s i f y 381; s t r a i n s o f S . ty p h im u riu m i s o l a t e d from man an d d i f f e r e n t
k in d s o f a n im a ls i n s e v e r a l E u ro p e a n c o u n t r i e s , t h e U n ite d S t a t e s ,
A r g e n tin a an d S o u th A f r i c a .

W ith a c o m b in a tio n o f 11 o f t h e p h a g e s u s e d

o r t e s t e d , 365 o f t h e s t r a i n s ex am in ed c o u ld b e d i v i d e d i n t o 21 t y p e s .
S t r a i n s r e l a t e d i n e p id e m io lo g i c a l o r e p i z o o t i o l o g i c a l r e s p e c t s an d a l s o
s t r a i n s i s o l a t e d fro m th e same i n d i v i d u a l r e a c t e d to th e same ty p e o f
phage .

R e p r e s e n t a t i v e s o f a l l th e s t r a i n s o f t h e o rg a n is m w ere ex am ined

a f t e r p a s s a g e s th r o u g h m ic e , an d t h e ty p e s w ere th e n fo u n d t o b e c o n s t a n t .
F a r t h e r in f o r m a t i o n r e g a r d i n g th e s t a b i l i t y o r u n i f o r m i t y o f some ty p e s
is

s t i l l re q u ire d .
M cC lure and C r o s s l e y (5 9 ) n o te d t h a t S a lm o n e lla n e w p o rt was r e ­

s p o n s i b l e f o r a n o u t b r e a k ,o f a c u t e g a s t r o e n t e r i t i s i n a g e n e r a l h o s p i t a l
i n v o l v i n g 75 c a s e s .

The i n c u b a t i o n p e r i o d was 1 2 -1 8 h o u r s .

p e c te d fo o d w as c o ld b e e f .

The s u s ­

S in c e th e c h e f an d t h e h e l p e r who w ere n o t

i l l h ad S . n e w p o rt i n t h e i r f e c e s , th e y m ig h t h a v e b e e n c a r r i e r s .
Crowe (1 2 ) d e s c r i b e d a n o u tb r e a k o f f o o d p o is o n in g due to S a lm o n e lla
a e r t r y c k e from a h e n ! s e g g , w h ic h i s a n u n u s u a l s o u rc e o f th e o r g a n is m .

25

F o o d s a f f e c t e d and so u r ce o f i n f e c t i o n
As Dolman (2 ? ) h as p o in t e d o u t , modes o f con veyan ce o f S a lm o n e lla
fo o d i n f e c t i o n s a r e p o t e n t i a l l y v e r y numerous b u t r a th e r seld om r e v e a le d ,
ow ing t o th e in c o m p le te n e s s o f th e e p id e m io lo g ic a l i n v e s t i g a t i o n s con­
d u cted .

Savage (7 5 ) l i s t e d th e c h i e f modes *of co n v ey a n ce a s consum p tion

o f th e m e a t, m il k , o r e g g s o f i n f e c t e d a n im a ls and p o l l u t i o n o f fo o d by
human c a r r i e r s , o r by i n f e c t e d r a t s and m ic e .

From, t h i s can be s e e n

t h e u n d e r - e s tim a tio n o f th e human c a r r i e r , th e f l y , and th e v a r i e t y o f
a n im a l r e s e r v o i r s f o r S a lm o n e lla o rg a n ism s d i s c l o s e d i n r e c e n t y e a r s .
The u s e o f b r i l l i a n t g r e e n , t e t r a t h i o n a t e b r o t h , b is m u th s u l f a t e a g a r ,
S . S . A g a r , d e s o x y c h o la te c i t r a t e a g a r , an d H ynes medium i s r e v e a l i n g a
h ig h e r i n c i d e n c e o f S a lm o n e lla c a r r i e r s t h a n was f o r m e r ly s u s p e c t e d .

N ot

o n ly a r e t h e r e h e a l t h y c a r r i e r s to c o n te n d w i t h , b u t some ty p e s o f
S a lm o n e lla i n f e c t i o n may g iv e r i s e to c l i n i c a l syndrom es so m ild a s to
p a ss u n n o tic e d .

M o re o v e r, t h e c o n v a le s c e n t c a r r i e r s t a t e may p e r s i s t

lo n g e r a f t e r fo o d b o rn e S a lm o n e lla i n f e c t i o n t h a n h a s b e e n g e n e r a l l y
b e l i e v e d a s p o i n t e d o u t by M osher e t a l . ( 6 6 ) .
The s p e c i a l l i a b i l i t y o f r a t s an d m ice t o s u c h i n f e c t i o n h a s lo n g
b e e n e s t a b l i s h e d , b u t i t now a p p e a rs t h a t t h e h o r s e , cow , s h e e p , p i g ,
g o a t , d o g , c a t , t u r k e y , d u c k , an d c h ic k e n a r e s u b j e c t to S a lm o n e lla
i n f e c t i o n o f g r e a t e r o r l e s s e r s e v e r i t y w h ic h m a n i f e s t s i t s p r e s e n c e by
s e p t i c e m i a , a b o r t i o n , g a s t r o e n t e r i t i s , o r b y some o t h e r a i l m e n t s .
J e n s e n (U8) , i n s t u d i e s on J4l9,000 hams an d 1|.,G00 p i c n i c s h o u l d e r s ,
e n c o u n te r e d no fo o d p o is o n in g t y p e s o f m ic r o o r g a n is m s , a n d , t h e r e f o r e ,
fo o d p o is o n in g in c i d e n c e s from f r e s h p o r k s h o u ld b e v e r y r a r e .

H o w ev er,

26

a p p a r e n t l y n o rm a l h o g s s l a u g h t e r e d f o r t h e m a rk e t h a v e b e e n fo u n d to
h a r b o r S a lm o n e lla i n t h e i r m e s e n t e r i c lym ph n o d e s , up to hi .9 p e r c e n t
(1 8 ) .

The s p e c i e s fo u n d a r e S . ty p h im u riu m , S . c h o l e r ^ e s u i s v a r .

K u n z e n d o rf, S . o r e g o n , S . a n a tu m , S . g i v e , S . b a r e i l l y , S . d e r b y ,
S . new b r u n s w ic k , S . b r e d e n e y , S . e n t e r i t i d i s , S . l e x i n g t o n , S . n e w in g to n ,
a n d S . W o r th in g to n .

T h is h ig h p e r c e n ta g e may a ls o b e due i n p a r t a t

l e a s t to f e c a l c o n t a m i n a t i o n .
C h e r ry e t a l . (9 ) fo u n d t h a t S a lm o n e lla may b e fo u n d i n r e t a i l
m a rk e t m e a t s .

O f 250 m e a t sa m p le s w h ic h w ere e x a m in e d , 13 ( 5 . 2 p e r c e n t )

y i e l d e d S a lm o n e lla .

Of t h e 170 p o r k p r o d u c ts w h ic h w ere e x a m in e d , 10

( 5 . 9 p e r c e n t ) y i e l d e d S a lm o n e lla .
i n p o rk p ro d u c ts th a n i n b e e f .
is o la te d :

The in c id e n c e w as fo u n d t o b e g r e a t e r

The f o l l o w i n g t y p e s o f S a lm o n e lla w ere

S . ty p h im u r iu m , S . g i v e , S . d e r b y , S . a n a tu m , S . n e w p o r t,

S . b r e d e n e y , S . s e n f t e n b e r g , and S . n e w in g to n .

The m ost p r o b a b le so u r ce

o f th e S a lm o n e lla was e v i d e n t l y th e a n im a ls from w hich th e m ea ts were
o b t a in e d .
An e x a m in a tio n f o r th e p r e s e n c e o f S a lm o n e lla i n v a r i o u s fo o d s
p u r c h a s e d o n th e o p e n m a rk e t i n I l l i n o i s ( 3 l ) ?gave t h e f o l l o w i n g r e s u l t s :
S a lm o n e lla was p r e s e n t i n 0 . 6 p e r c e n t o f
c e n t o f p o w dered

500 s h e l l e g g s and i n 3 .0 p e r

eg g s a m p le s ; i n 0 .2 p e r c e n t o f . 5 l 2

b e e f s a m p le s ; i n

1 7 .6 p e r c e n t o f 102 sa m p le s o f h am b u rg er h a s h ; i n 0 . 9 p e r c e n t o f 327
p o u l t r y c a r c a s s e s o f "U . S . I n s p e c t e d '1 g ra d e an d I n 1 0 .8 p e r c e n t o f 7I4.8
u n i n s p e c t e d b i r d s ; i n l l u 3 p e r c e n t o f 573 "U . S . I n s p e c t e d an d p a s s e d "
p o r k sa m p le s an d

i n 2 6 .8 p e r c e n t o f 101 u n in s p e c te d

The ty p e s

o f S a lm o n e lla w h ich were r ec o r d e d i n

p o r k s a m p le s .
d e t a i l In clu d ed

S . typ h im u riu m , S . o r a n ie n b u r g , S . b a r e i l l y , S . n ew p o rt, and a number o f

27

o t h e r s p e c i e s com m only a s s o c i a t e d w ith f o o d p o i s o n i n g .
w as f r e q u e n t l y fo u n d i n t h e p o r k an d h a m b u rg e r s a m p le s .

S. c h o le r a e s u is
W ith t h e e x ­

c e p t i o n o f S . p u llo r u m w h ic h w as n o t uncommon i n f o w l s , t h e d i s t r i b u t i o n
o f S a lm o n e lla i n human i n f e c t i o n s i n t h e h o s p i t a l s s e r v i n g t h e a r e a s i n
w h ic h t h e fo o d w as on s a l e w as v e r y s i m i l a r to t h e p r e v a l e n c e i n t h e
p o u l t r y , a n o b s e r v a t i o n n o te d i n s e v e r a l p r e v i o u s s u r v e y s i n th e U n ite d
S ta te s .

One o f t h e d e t a i l e d f i n d i n g s o f i n t e r e s t w as t h e f r e q u e n c y o f

S . c h o l e r a e s u i s i n t h e b r a i n s , c h o p s , an d l i v e r s o f h o g s e v e n i n t h e
i n s p e c t e d s a m p le s .

T h e re w as e v i d e n c e , h o w e v e r, t h a t t h i s o rg a n is m i s

m ore r e a d i l y k i l l e d b y h e a t t h a n c e r t a i n o t h e r s a lm o n e lla e ( 31 ) .
B d r n s t e i n and S ap h a ( 3 ) r e p o r t e d human i n f e c t i o n due t o S . s a i n t
p a u l , f i r s t i s o l a t e d fro m t u r k e y s , an d t o S . w o r t h i n g t o n , S . u r b a n a , and
S . m a n h a t ta n , a l l h i t h e r t o r e g a r d e d a s fo w l r a t h e r t h a n human p a th o g e n s ,
w h ile t h e r e h ave b e e n s e v e r a l r e p o r t s o f f o o d p o i s o n i n g 'f r o m d uck e g g s
fo u n d t o b e i n f e c t e d w ith S . e n t e r i t i d i s an d S , ty p h im u riu m .

S . b re d e n e y

h a s b e e n i s o l a t e d n o t o n ly fro m m an, b u t h a s a l s o b e e n i s o l a t e d , a c c o r d in g
t o H inshaw e t a l . (i|2 ) from n o rm a l sw in e an d fro m a w id e v a r i e t y o f b i r d s ,
i n c l u d i n g t h e d u c k , t u r k e y , q u a i l , g u in e a f o w l , an d C h u g ar p a r t r i d g e .
Some i n v e s t i g a t i o n s a s s o c i a t e d w ith S a lm o n e lla
i n f e c t i o n o f fo o d s
S in c e t h e r e a r e r e l a t i v e l y fe w e r S a lm o n e lla fo o d i n f e c t i o n s t h a n
S ta p h y lo c o c c u s fo o d p o i s o n i n g s , i t i s o b v io u s t h a t t h e s e o rg a n is m s do n o t
s u r v i v e f o r a lo n g t i m e . o u t s i d e t h e i r n a t u r a l h o s t s i n m o st i n s t a n c e s ,
e x c e p t i n c e r t a i n a d a p t a t i o n s a s w i l l b e m e n tio n e d u n d e r t h e d i s c u s s i o n .
T h i s i s i n s h a r p c o n t r a s t t o th e common o c c u r r e n c e o f S ta p h y lo c o c c u s fo o d
p o i s o n i n g o u t b r e a k s , w h ich a r e p r o b a b ly due to t h e u b i q u i t y o f t h e S ta p h y lo ­
coccus in n a tu re .

28

S a lm o n e lla g e n e r a l l y grow s a t te m p e r a tu r e s r a n g i n g fro m 2 1 .1 - 3 6 .7 C
( 7 0 - 9 8 F ) , an d a f t e r a two h o u r p e r i o d a t 3 7 -2 C (9 9 F ) r e p r o d u c e s e v e r y
1 5 m in u te s (k 8 ) .
L a n e -C la y p o n ( 5 6 ) , u s in g E . c o l i , S . t y p h o s a , an d S . e n t e r i t i d i s ,
h a s f o u n d t h a t w hen a f r e s h b r o t h c u l t u r e i s made w i th a s m a ll in o c u lu m
t h e r e i s a p e r i o d d u r i n g w h ich t h e r e i s no i n c r e a s e i n t h e num ber o f
b a c te ria p re s e n t ( i n i t i a l s ta tio n a ry p h a se ).

H ow ever, w hen t h i s p e r i o d

i s o v e r t h e b a c t e r i a commence to d i v i d e r e g u l a r l y ( l o g a r i t h m i c g ro w th
p h a s e ) ; t h i s i s shown b y t h e f a c t t h a t t h e l o g a r i t h m s o f t h e num bers
p l o t t e d a g a i n s t tim e a r e fo u n d t o f a l l o n a s t r a i g h t l i n e .

T h is r e g u l a r

g ro w th p e r s i s t s u n t i l ( o r n e a r l y - u n t i l ) a maximum h a s b e e n r e a c h e d , a f t e r
w h ic h t h e num bers re m a in m ore o r l e s s c o n s t a n t (maximum s t a t i o n a r y p h a s e )
an d th e n s lo w ly d e c l i n e ( l o g a r i t h m i c d e a th p h a s e ) .

T h is i s o f p r a c t i c a l

im p o r ta n c e i n t h a t t h e g r e a t e r t h e d o s e o f S a lm o n e lla s w a llo w e d , t h e m ore
a c u te a r e t h e sym ptom s and t h e s h o r t e r t h e p e r i o d o f

o n s e t o f symptoms

(1+8) , p r o v i d i n g o f c o u r s e t h a t t h e s t r a i n i s v i r u l e n t .
An i n c r e a s i n g am ount o f e v id e n c e h a s a c c u m u la te d r e l a t i n g t o th e
c o n ta m in a ti o n o f s p r a y - d r i e d w hole egg pow der w it h S a lm o n e lla ; G ibbons
an d M oore (3 k ) 3 S c h n e id e r ( 7 6 , 77) , an d Solow ey e t a l , ( 8 3 , 81+).

D u rin g

W o rld W ar I I d r i e d e g g s w e re s h ip p e d i n l a r g e q u a n t i t i e s to E u r o p e , and
o f 7,581+ s a m p le s fro m t h e U n ite d S t a t e s , C a n a d a , an d A r g e n tin a 75k o r
9 .9 p e r c e n t w e re fo u n d to c o n t a i n s a l m o n e l l a e , o f w h ic h 33 s p e c i e s w ere
i d e n t i f i e d (1 8 ) ,

T h is e v id e n c e p o i n t s t o th e p o s s i b l e o c c u r r e n c e o f

S a lm o n e lla fo o d i n f e c t i o n fro m s u c h p r o d u c t s .
The d e m o n s tr a te d a b i l i t y o f S a lm o n e lla t o m u l t i p l y r a p i d l y i n
r e c o n s t i t u t e d e g g s a t a te jp p e r a tu r e o f 2 5 -k 5 C (7 7 -1 1 3 F ) , t o g e t h e r

29

w i t h t h e f a c t t h a t t h e s e o rg a n is m s may f r e q u e n t l y s u r v iv e s c r a m b lin g
t e m p e r a t u r e , p o i n t to t h e d e s i r a b i l i t y o f u s i n g eg g p ow der im m e d ia te ly
a f te r i t s re c o n s titu tio n (8 9 ).
S a lm o n e lla ty p h im u riu m an d S . e n t e r i t l d i s , i s o l a t e d fro m n a t u r a l l y
i n f e c t e d d u c k e g g s an d i n o c u l a t e d i n t o th e y o lk o f d uck e g g s w e ig h in g
9 7 -1 0 9 gm, c o u ld b e r e c o v e r e d i n c u l t u r e fro m some o f t h e e g g s a f t e r
t h e y h a d b e e n im m ersed i n b o i l i n g w a te r f o r up t o 13 m in u te s (1 0 ) .
R e t t g e r e t a l . (7 2 ) fo u n d t h a t s o f t b o i l i n g , c o d d l i n g , and f r y i n g
o n one s i d e o n ly do n o t n e c e s s a r i l y r e n d e r t h e y o lk o f i n f e c t e d e g g s
f r e e fro m v i a b l e S . p u llo r u m .
S t a f s e t h e t a l , (8 7 ) fo u n d t h a t some s p e c i e s o f s a lm o n e lla e c o u ld
s u r v i v e i n e g g s s t o r e d a t 29 C ;

o v e r a p e r i o d o f 12 m o n th s .

s t a t e d t h a t b y o r d i n a r y m e th o d s o f c o o k in g s

They a l s o

b o i l i n g , f r y i n g , p o a c h in g ,

a n d s c r a m b li n g , S . p u llo r u m f r e q u e n t l y a n i n h a b i t a n t o f e g g s , w as n o t
a lw a y s d e s t r o y e d .

T hey recom m ended s c ra m b le d o r f o u r - m in u te b o i l e d e g g s

a s th e s a f e s t .
An i n v e s t i g a t i o n b y H ussem ann and W a lla c e (1|6) r e v e a le d t h a t c u r ­
r e n t l y a c c e p te d m e th o d s o f b r o i l i n g o r r o a s t i n g m a rk e d ly re d u c e t h e
num ber o f S a lm o n e lla p r e s e n t i n c h ic k e n m u s c le o r l i v e r , b u t do n o t
r e n d e r a c h ic k e n s t e r i l e o f t h e o rg a n is m .
P r o p e r l y p r e p a r e d c u s t a r d s i n n o rm a l p r a c t i c e w i l l b e e s s e n t i a l l y
s t e r i l e i n r e l a t i o n to S a lm o n e lla e n t e r i t i d i s an d S ta p h y lo c o c c u s a u r e u s
a s t h e y l e a v e t h e c o o k in g k e t t l e o r t h e b a k in g o v e n , i n t h e c a s e o f b a k e d
c u s ta rd p ie s ( 7 ) .

30

T he p r o d u c t i o n o f " t o x i n " b y S a lm o n e lla
S av ag e C7U) r e p o r t e d i 'I n some c a s e s th e l i v i n g i n f e c t i v e b a c i l l i
a r e i n g e s t e d w ith t h e f o o d w ith none o r b u t l i t t l e

o f t h e i r to x ic p ro d u c ts .

I n such c a s e s th e in c u b a tio n p e rio d w i l l be o f a p p re c ia b le d u r a tio n s in c e
tim e m u st e l a p s e b e f o r e th e b a c i l l i c a n m a n u fa c tu r e s u f f i c i e n t t o x i n s to
m a n i f e s t sym ptom s.

I n o t h e r c a s e s t h e b a c i l l i may b e k i l l e d d u r in g th e

p r o c e s s o f m a n u fa c tu r e o r p r e p a r a t i o n f o r t h e t a b l e , an d o n ly t h e h e a t
r e s i s t i n g to x ic p ro d u c ts w i l l be l e f t .

T h e se , b e in g p re fo rm e d , w i l l

e x e r t t h e i r p o is o n o u s p r o p e r t i e s r a p i d l y .

The m a j o r i t y o f o u tb r e a k s m u st

b e lo o k e d u p o n a s b e in g c a u s e d b y a m ix tu r e o f b a c i l l i and t o x i n s , t h e
b a c i l l i h a v in g h a d tim e to grow i n t h e fo o d b e f o r e th e y w ere c o n su m ed ."
S in c e t h i s r e p o r t i n 1 9 2 0 , r e p e a t e d i n v e s t i g a t i o n s b y many w o rk e rs
h a v e b e e n made t o p r o v e o r d is p r o v e t h i s t h e o r y .

The r e p o r t s o f some o f

t h e e a r l y w o r k e r s , who showed t o x i c i t y f o r some l a b o r a t o r y a n im a ls o n
i n j e c t i o n s w ith h e a t e d f i l t r a t e s , c a n be su m m arized b y t h e s ta t e m e n t
t h a t c e r t a i n h e a t s t a b l e s o l u b l e s o m a tic a n t i g e n s o f t h e S a lm o n e lla g ro u p
a r e l i a b l e to b e t o x i c f o r some s p e c i e s o f l a b o r a t o r y a n im a ls when i n ­
j e c t e d i n t o t h e i r b lo o d s tr e a m .

I n g e n e ra l th e v a rio u s r e p o r ts d a tin g

fro m 1 9 2 0 -3 5 i n d i c a t e t h a t s u i t a b l y p r e p a r e d f i l t r a t e s o r h e a t k i l l e d
c u l t u r e s o f some s t r a i n s o f c e r t a i n ty p e s o f S a lm o n e lla may c o n t a i n f a c t o r s
w h ic h a r e t o x i c f o r some s p e c i e s o f l a b o r a t o r y a n i m a l s .

The t o x i c e f f e c t s

m a n i f e s t e d , when s u c h p r e p a r a t i o n s a r e i n j e c t e d i n t r a v e n o u s l y an d t h o s e
w h ic h f o l l o w o r a l a d m i n i s t r a t i o n , a r e p r o b a b ly due to q u i t e d i f f e r e n t
f a c t o r s ; an d t h e r e i s no e v id e n c e s u g g e s tin g t h a t e i t h e r ty p e o f t o x i c
e f f e c t s i s a n a lo g o u s to t h e " t o x i n " ty p e o f f o o d p o i s o n in g i n m an.

31

D ack e t a l . (1 8 ) and V e rd e r an d S u tt o n (9 2 ) show ed b y e x p e r im e n ta ­
t i o n t h a t f i l t r a t e s o r h e a t s ta b l e p ro d u c ts o f f r e s h l y i s o l a t e d c u l t u r e s
o f S a lm o n e lla e n t e r i t i d i s . a f t e r p a s s a g e th r o u g h m an, a r e h a r m le s s w hen
f e d t o m an, a n d t h a t v i a b l e o rg a n is m s a r e n e c e s s a r y t o c a u s e i n f e c t i o n
and i l l n e s s .
R e u te r (7 3 ) fo u n d t h a t none o f 39 S a lm o n e lla c u l t u r e s c o u ld s ta n d
h e a t i n g a t 80 C f o r more t h a n a few m o m en ts.

E ig h ty m in u te s a t 70 C o r ..

f o u r h o u r s a t 69 C w as s u f f i c i e n t to s t e r i l i z e a l l t h e c u l t u r e s .

H eat

s t a b l e e n d o to x in c o u ld n o t b e d e m o n s tra te d i n an y o f t h e s e c u l t u r e s w h ich
i n c l u d e d s i x S . e n t e r i t i d i s s t r a i n s , e i t h e r i n l a b o r a t o r y a n im a ls o r
w hen t h e a u t h o r h i m s e l f i n g e s t e d b o i l e d c u l t u r e s o r a r t i f i c i a l l y i n f e c t e d
b o i l e d m e a t.

He i n f e r r e d , t h e r e f o r e , t h a t m e at p o is o n i n g th r o u g h o r g a n ­

is m s o f t h e S a lm o n e lla g ro u p c a n o c c u r o n ly i f l i v i n g o rg a n is m s a r e
p re s e n t.
f

A lth o u g h a f a r g r e a t e r num ber o f n e g a t i v e human f e e d i n g e x p e r i ­
m e n ts , i n v o l v i n g a w id e r v a r i e t y o f ty p e s o f S a lm o n e lla an d u s in g f r e s h l y
i s o l a t e d s t r a i n s , w ou ld n eed t o b e c a r r i e d o u t b e f o r e t h e c a t e g o r i c a l
c la i m c o u ld b e made t h a t a " to x in * 1 ty p e o f S a lm o n e lla f o o d p o is o n in g c a n
n o t o c c u r , t h e a v a i l a b l e e v id e n c e t o d a te d o e s n o t s u g g e s t t h a t S a v a g e * s
h y p o t h e s i s a c c o u n ts f o r an y s i g n i f i c a n t p r o p o r t i o n o f s u c h o u t b r e a k s ,
a c c o r d in g t o Dolm an (2 7 ) .
J e n s e n (1+8) h a s s t a t e d c o n c l u s i v e l y t h a t i n t h e c a s e o f p a r a ­
ty p h o i d ty p e o f fo o d p o i s o n i n g , t h e p a r a t y p h o i d b a c i l l u s d o e s n o t fo rm
a . t o x i n b u t i n f e c t s t h e b ow el d i r e c t l y .

I t was shown i n t h e c o u r s e o f

e p id e m ic t h a t o n ly th o s e p e o p le who a t e u n c o o k ed o r sem ic o o k e d m e at b e ­
came i l l , w h e re a s th o s e who a t e c o o k ed m e at d i d n o t becom e i l l .

32

Symptoms
B ack (1 8 ) s t a t e d t h a t t h e symptoms o f S a lm o n e lla g a s t r o i n t e s t i n a l
i n f e c t i o n a r e c h a r a c t e r i z e d b y n a u s e a , v o m itin g , a b d o m in a l p a i r f , an d
d ia rrh e a .

The o n s e t i s u s u a l l y s u d d e n .

w i t h a h e a d a c h e an d c h i l l .

The a t t a c k may b e u s h e r e d i n

The a b d o m in a l p a i n i s o f t e n t h e f i r s t symptom

and i t may b e g r i p i n g a n d s e v e r e , t o g e t h e r w i th p e r s i s t e n t f o u l s m e llin g
d ia rrh e a .

L a t e r i n t h e a t t a c k t h e s t o o l s may b e w a te r y an d so m etim es o f

g re e n is h c o lo r .
a r e m a rk e d .

P r o s t r a t i o n s , m u s c u la r w e a k n e s s , f a i n t n e s s a n d t h i r s t

T h e re i s a lm o s t a lw a y s a r i s e i n te m p e r a tu r e w i t h v a r io u s

n e rv o u s m a h i f e s t a t i o n s o f r e s t l e s s n e s s , m u s c u la r t w i t c h i n g s a n d d r o w s i­
n ess .

O l i g u r i a may b e p r e s e n t an d h e r p e s f r e q u e n t l y f o l l o w s .
D olm an (2 7 ) l i s t e d t h r e e m a in c l i n i c a l fo rm s o f human S a lm o n e lla
a

in f e c t i o n a s fo llo w s :

1.

A c u te g a s t r o i n t e s t i n a l i r r i t a t i o n , 2 . T y p h o id a l

sy n d ro m e , 3 . B lo o d s tr e a m i n f e c t i o n .

The i n c u b a t i o n p e r i o d i s 1 2 -3 6

h o u r s a f t e r w h ic h t h e r e i s a su d d e n o n s e t o f v o m itin g , d i a r r h e a , a n d
a b d o m in a l p a i n , a c c o m p a n ie d b y f e v e r an d p r o s t r a t i o n .

T he a b d o m in a l p a i n

an d d i a r r h e a a r e o f t e n s e v e r e , b u t th e i l l n e s s i s t y p i c a l l y o v e r i n a
few d a y s , a lth o u g h so m etim es o f l o n g e r d u r a t i o n . T h e re i s a n a p p r e c i a b l e
\
m o r t a l i t y r a t e o f 1 - 2 p e r c e n t . I n an a c u t e o u tb r e a k t h e c a u s a l
S a lm o n e lla i s o f t e n r e c o v e r a b l e fro m t h e f e c e s o f p a t i e n t s w it h c h a r ­
a c t e r i s t i c sym ptom s, a n d may a l s o b e i s o l a t e d o c c a s i o n a l l y fro m e x p o se d
p e r s o n s who h av e re m a in e d sy m p to m le ss o r w hose o n ly c o m p la in t may b e
s lig h t d ia rrh e a .

33

The c o n t r o l o f S a lm o n e lla fo o d i n f e c t i o n

I n s p i t e o f t h e f a c t t h a t r e l a t i v e l y s m a ll num ber o f c a s e s a r e
r e p o r te d , th e c o n tr o l o f t h i s ty p e o f i n f e c t i o n o f f e r s c o n s id e ra b le
d i f f i c u l t y and i s o f no mean i m p o r ta n c e .

One h a s t o c o n s i d e r a l s o t h a t

o rg a n is m s o f t h i s t y p e a r e w id e ly fo u n d i n n a t u r e , so f a r a s n a t u r a l
h o s t s a r e c o n c e r n e d , a n d t h a t ty p h o id f e v e r i s a ls o c a u s e d b y S a lm o n e lla
ty p h o s a .
O s t r o l e n k an d W elc h (? 0 ) showed t h a t t h e h o u se f l y , Muse a domes t i c a ,
w as r e s p o n s i b l e f o r s p r e a d in g e n t e r i c d i s e a s e s , an d S . e n t e r i t i d i s
was fo u n d to s u r v i v e i n t h e f l y f o r t h e d u r a t i o n o f i t s l i f e , a p p r o x i ­
m a te ly f o u r w e e k s .

The o rg a n is m c o u ld b e fo u n d i n m a g g o ts , p u p a e , an d

a d u l t f l i . e s com ing i n s e q u e n c e from c o n ta m in a te d f l y e g g s .

In c o n tra s t

to t h e s i g n i f i c a n c e o f r a t s a n d m ice a s v e c t o r s o f fo o d p o is o n in g o r g a n ­
is m s , t h e h o u se f l y a p p e a rs to b e much m ore im p o r ta n t i n fo o d p l a n t
s a n ita tio n .

T r a n s f e r o f S . e n t e r i t i d i s i n f e c t i o n fro m i n f e c t e d f l i e s to

m ic e a n d t h e r e t r a n s f e r o f i n f e c t i o n from, i n f e c t e d m ic e to f l i e s w ere
a l so demo n s t r a t e d .
E s k e y e t a l . ( 29 ) d e m o n s tr a te d t h a t th e two common r a t f l e a s ,
X e n o p s y lla c h e o p is an d N o s o p s y llu s f a s c i a t u s may be i n f e c t e d w ith
S . e n t e r i t i d i s when f e e d in g on i n f e c t e d m ic e , an d t h a t th e f l e a s may
t r a n s m i t th e i n f e c t i o n from one mouse to a n o th e r by t h e i r b i t e s .

F u rth e r­

m o re , th e f e c e s o f i n f e c t e d f l e a s a ls o c o n t a i n v i a b l e o rg a n is m s i n l a r g e
n um bers an d p r o v id e a n a d d i t i o n a l m eans b y w h ich th e I n f e c t i o n may be
d is s e m in a te d .

Many f l e a s becom e f r e e o f th e I n f e c t i o n , b u t o v e r h a l f o f

3h

them rem ain in f e c t e d u n t i l d e a th .

S . e n t e r i t i d i s in f e c t i o n appears

to produce c e r t a in p a t h o lo g ic a l c o n d itio n s i n th e a lim en ta ry ca n a l o f
f l e a s t h a t ten d to sh o r te n th e l i v e s o f many o f them.
f l e a s su r v iv e d th e i n f e c t i o n f o r more than two months

However, some
.

Meat I n s p e c tio n law s i n Canada and th e U n ited S t a te s seem to
have done much i n p r e v e n tin g th e spread o f S a lm o n e lla .
in g u n it s have played' an im portant p a r t .

A lso r e f r i g e r a t ­

T h is seems e v id e n t when th e

number o f ou tb reak s i n Europe i s compared w ith th o se i n th e above two
c o u n t r ie s .

However, a s m en tion ed, s t a t i s t i c s reg a rd in g such in c id e n c e s

may n ot r e p r e s e n t a c tu a l c a s e s , because many u n id e n t if ie d c a s e s may p a ss
f o r common g a s t r o in t e s t in a l u p s e ts o f obscure e t i o l o g y .

The c o n tr o l o f

r o d e n ts i s a ls o an im portant phase o f th e work i n p r e v e n tin g fo o d
i n f e c t i o n o f t h i s t y p e , ar^d th e house f l y must be e r a d ic a te d .

M ilk and

c h e e se may become contam inated from a d is e a s e d cow or subsequent hand­
lin g ,

• P a s te u r iz a tio n o f m ilk i s e f f e c t i v e i n d e s tr o y in g S a lm o n e lla .

I t must be remembered th a t i n t h i s typ e o f S alm on ella i n f e c t io n th e
organism s are p a th o g en ic f o r a n im a ls, producing i n anim als a d is e a s e
s im ila r to ty p h o id f e v e r i n man, and are d if f e r e n t o n ly from th e p ath o­
g e n ic forms a tta c k in g man.
S in c e th e r e are many ways and m eans, by which meats can be con­
tam in ated on th e su r fa c e w ith S a lm o n e lla , th e c o n tr o l o f such in c id e n c e
by th e u se o f a ch em ical agen t i s th e g o a l o f t h i s i n v e s t i g a t i o n .
S a lm o n ella i n f e c t i o n , i s o f t e n associated .~ w ith ^meat 'p o iso n in g '1,
and a ch em ica l which w i l l i n h i b i t fo o d p o iso n in g organism s on meat should
be v a lu a b le , b ecau se n ot o n ly can i t be used to t r e a t meat s o ld w ith o u t

3f?

r e f r i g e r a t i o n b u t i t c a n a l s o b e u s e d to t r e a t m a rk e t m e at b e f o r e i t i s
re frig e ra te d .

R e f r i g e r a t i o n , a s a f o r e m e n tio n e d , i s n o t an e f f e c t i v e

way o f d e s t r o y i n g f o o d p o i s o n i n g o r g a n is m s .
F o r v e r y p r a c t i c a l p r o c e d u r e s o f d e t e c t i o n and i s o l a t i o n o f fo o d
p o i s o n i n g o rg a n is m s fro m d a i r y p r o d u c t s , a c o n c is e a r t i c l e b y Newman
( 67 ) i s recom m ended.

36

E f f e c t s o f some, common ch em ica ls on
food p o is o n in g organism s
An i n v e s t i g a t i o n by V o e g e li (9 3 ) r e v e a le d t h a t c u t t in g u t e n s i l s
are r e s p o n s ib le to a g r e a t e x te n t f o r b a c t e r ia l con tam in ation o f p r e ­
packaged f r e s h m eat.

Mallmann and C h u r c h ill ( 6 l ) , i n t h e ir a r t i c l e on

th e c o n tr o l o f m icroorganism s in food sto r a g e room s, s ta te d “I f we are
to c o n tr o l th e developm ent o f m icroorganism s on th e su r fa c e o f b e e f
d u rin g sh o r t tim e s to r a g e , th en e it h e r u l t r a v i o l e t l i g h t or carbon
d io x id e atmosphere may answer th e purpose e f f e c t i v e l y .

I f m icroorganism s

are co n ta m in a tin g food produce through c o n ta c ts w ith u t e n s i l s , t a b le
s u r f a c e s , e t c . th en a ch em ical s a n i t iz e r i s in d ic a t e d .

I f con tam in ation

on w a ll and f l o o r s u r fa c e s i s a source o f tr o u b le , th en a ch em ical a g e n t,
p r e fe r a b ly w ith r e s id u a l a c t i v i t y , should be s e le c t e d ."

"Because th e

q u artern ary compounds e x h ib it c o n sid e r a b le b a c t e r i o s t a t ic a c t io n on
s p o r e s , i t would seem th a t th e s e compounds would be p r e fe r a b le f o r use
fo llo w in g good c le a n in g in p refe r e n c e to th e h y p o c h lo r ite s ."
Hucker and Haynes (14!) found th a t, i n v e a l b roth , a c e t ic a c id i n
c o n c e n tr a tio n a s low a s 0 .1 9 p er ce n t c a n ,b r in g about a d ecid ed r e d u c tio n
i n th e number o f fo o d p o iso n in g s ta p h y lo c o c c i in 48 h o u rs, and a t th e
end o f sev en days media c o n ta in in g 0 .2 - 0 .3 p er ce n t o f th e a c id were
p r a c t i c a l l y f r e e o f o rg a n ism s.

Hence a c e t ic a c id has an in h ib it in g

e f f e c t i n low c o n c e n tr a tio n and a d e f in i t e k i l l i n g e f f e c t i n h ig h er con­
c e n t r a tio n s .

37

I n s t u d i e s on fo o d p o is o n in g s t a p h y lo c o c c i by Nunheimer and
F a b ia n ( 6 8 ) , a c e t i c a c id h as been fo u n d to p o s s e s s a marked g e r m ic id a l
i

power i n com p arison to some commonly o c c u r r in g o r g a n ic a c id s i n fo o d s a s
w e l l a s h y d r o c h lo r ic a c i d .

The o r d e r i s a c e t i c , c i t r i c , l a c t i c , m a lic ,

t a r t a r i c and h y d r o c h lo r ic a c i d s .

The d e c r e a s in g o rd er o f a n t i s e p t i c a c t i o n

was fou n d to be a c e t i c , l a c t i c , c i t r i c , m a li c , t a r t a r i c and h y d r o c h lo r ic
a c id s .

I n t h i s s tu d y s t r e s s was p la c e d upon fo o d p o is o n in g s t a p h y l o c o c c i .
L ev in e and F e l l e r s (57) , i n t h e i r s tu d y o f th e e f f e c t o f a c e t i c

a c id on m icro o rg a n ism s r e l a t e d to fo o d s p o i l a g e , fou n d t h a t a c e t i c a c id
p o s s e s s e s t o x i c i t y f o r b a c t e r ia i n e x c e s s o f t h a t w h ich can be a t t r ib u t e d
to pH a l o n e .

The i n h i b i t i n g and l e t h a l a c t io n o f a c e t i c a c id i s v e r y

p ro n o u n ced .
INHIBITING AND LETHAL CONCENTRATIONS OF ACETIC ACID
( A f t e r L ev in e and F e l l e r s )

Organism

I n h ib itin g
pH

I n h ib itin g
A c id ity

L e th a l
pH

P er c e n t
)

S a lm o n e lla a e r tr y c k e
S ta p h y lo c o c c u s au reu s
Phytom onas p h a s e o li
B a c illu s cereus
B a c i l l u s m e s e n te r ic u s
Saccharom yces c e r e v is a e
A s p e r g i l l u s n ig e r

h.9
5.0
5,2 '
h.9
h.9
3.9
h .l

0.01+
0.03
0 .02
0 .02*

o.ol+
, 0.59
0.2 7

L e th a l
A c id ity
P er c e n t

4 .5
h .9
5 .2
h .9
h.9
3 .9
3.9

0 .0 9
o.ol+
0.02
o.oi*
0.01+
0 .5 9
o .5 9

D e h y d r o a c e tic a c id ( 3 - a c e t y l~ 6 ~ m e t h y l- l ,2 -p y r a n ~ 2 ,i+ (3 )d io n e ) and
i t s sodium s a l t have been u se d a s m y c o s ta tic a g e n ts on b r e a d , f r u i t s ,
v e g e t a b l e s , and d a ir y p r o d u c t s .

The compounds are r e l a t i v e l y n o n to x ic

38

(8 1 ,6 .6 ,9 8 ) at. c o n c e n tr a tio n s s u it a b le Tor u s e , and a t which th e y are a ls o
o d o r le s s , c o l o r l e s s , and t a s t e l e s s .

However, th e r e i s some d ecrea se i n

a n tim ic r o b ia l a c t i v i t y o f th e a c id and i t s sodium s a l t w ith an in c r e a s e
i n pH (§7) , and t h i s i s p rob ably one o f th e rea so n s why t h e ir u se to
c o n t r o l fo o d p o iso n in g organism s on meat i n t h i s i n v e s t ig a t io n was not
s a tis fa c to r y .

They are l e s s a c t iv e i n an a lk a lin e range than in an a c id

range .
INHIBITING CONCENTRATIONS OF DEHYDROACETIC ACID
(A fte r W olf)

T e st Organism

C o n cen tra tio n P er­
m it t in g Growth
(P er ce n t)

B a c illu s s u b t ilis
E s c h e r ic h ia c o l i
S alm on ella pullorum
S alm o n ella ty p h o sa
S ta p h y lo co ccu s aureus
S tre p to c o c c u s pyogenes

0 .2
0 .3
0 .2
0 .1
0 .2
0 .2

C on cen tration That
I n h ib it s Growth
(P er c e n t)
0 .3
o.U
0 .3
0 .2
0 .3
0 .3

Fabian and Bloom ( 30) found d ic h lo r a c e t ic a c id to be l e s s and t r i ­
c h lo r a c e t ic a c id s t i l l l e s s e f f e c t i v e th an m on och loracetic a c id in
p r e s e r v in g a c t i o n .

They a ls o found b en zoic a c id to in h i b it th e growth

o f m icroorganism s to about th e same e x te n t as m on och loracetic a c id under
p r a c t i c a l c o n d it io n s , and b o th ch em icals to be more e f f e c t i v e a g a in s t
y e a s t s than a c id producing b a c t e r ia .

The use o f m on och loracetic a c id i s

a l s o . p r o h ib ite d by th e Food and Drug A d m in istr a tio n , and i t s u t i l i t y in
th e U n ited S t a t e s i s th e r e fo r e n ot p o s s i b l e .

39

M cLean e t a l . (6 0 ) fo u n d t h a t c h lo r a m p h e n ic o l ( C h lo ro m y c e tin ) c a n
i n h i b i t many S a lm o n e lla s p e c i e s i n v i t r o a t 2 .5 u g . / m l . , an d r e s i s t a n t
s t r a i n s a t 5 .0 u g . / m l . i n t h e c u l t u r e m edium .

I t c a n i n h i b i t S ta p h y lo ­

c o c c u s i n t h e c o n c e n t r a t i o n o f 2 .5 -1 0 .0 u g . / r a l .
C h lo ra m p h e n ic o l h a s b e e n u s e d c l i n i c a l l y i n t h e t r e a t m e n t o f
f e v e r s o f t h e e n t e r i c g ro u p w ith s u c c e s s , an d s e v e r a l f a v o r a b l e r e p o r t s .
h a v e b e e n p u b l i s h e d i n v a r i o u s m e d ic a l j o u r n a l s .

R eview s i n many num bers

o f B u l l e t i n O f H y g ie n e r e v e a l i t s a p p r e c i a t i o n i n o t h e r c o u n t r i e s .
C h lo ra m p h e n ic o l ( C h lo r o m y c e tin ) , a u re o m y c in , a n d te r r a m y c in w ere
a d d ed r e s p e c t i v e l y t o f r e s h l y g ro u n d b e e f i n c o n c e n t r a t i o n s r a n g in g fro m
0 . 5 t o 2 .0 ppm and t h e i r e f f e c t n o te d o n t h e t o t a l b a c t e r i a l c o u n t a s
w e ll a s t h e k e e p in g q u a l i t y o f th e m e a t.

G round b e e f c o n t a i n i n g an y o f

t h e ab o v e a n t i b i o t i c s s p o i l e d a f t e r a p p r o x im a te ly 10 d a y s , w h ile t h e
c o n tr o ls s p o ile d a f t e r 5 d a y s.

N in e ty p e r c e n t o f t h e b e e f m i c r o f l o r a

s t u d i e d show ed m ark ed s u s c e p t i b i l i t y t o t h e above a n t i b i o t i c s ( 3 5 ) .

Uo

PART I .

GROWTH OF FOOD POISONING ORGANISMS ON BEEF AND PORK

In tro d u c tio n
I t i s g e n e r a l l y b e l i e v e d t h a t c o o k e d m e at i s m ore f a v o r a b l e to
b a c t e r i a l g ro w th t h a n f r e s h m e a t, p r o b a b ly due to t h e b r e a k i n g down o f
n u t r i e n t s t o m ore a s s i m i l a b l e f o r m s .

I t i s i n t e r e s t i n g , t h e r e f o r e , to

d e te r m in e t h e d i f f e r e n c e s i n g ro w th o f fo o d p o is o n in g s ta p h y l o c o c c i and
s a lm o n e lla e o n ra w b e e f an d p o r k , s p e c i a l l y o n raw l e a n m eat t a k e n fro m
t h e d e p th o f r e t a i l c u t s , on c o o k ed l e a n m e a t, an d on t h e s u r f a c e o f
ra w l e a n m e at p r e p a r e d an d h a n d le d i n r e t a i l t r a d e .
S in c e m e a t may b e c o n ta m in a te d o n t h e s u r f a c e w it h f o o d p o is o n ­
i n g s t a p h y l o c o c c i and s a lm o n e lla e fro m t h e tim e o f k i l l i n g t o s t o r a g e
and s a l e , t h i s i s a s tu d y o f th e v i a b i l i t y o f th e o rg a n is m s o n m e at k e p t
a t d i f f e r e n t a tm o s p h e r ic te m p e r a tu r e r a n g e s e x c l u s i v e o f a v e r y h ig h
ra n g e su c h a s 3 2 .2 - 3 7 .8 C (9 0 -1 0 0 F ) o r a low r a n g e su c h a s f r e e z i n g .
The p r e s e n t s tu d y w as c o n d u c te d t o d e te r m in e t h e optim um te m p e ra ­
t u r e r a n g e b e tw e e n t h e v e ry h ig h and lo w te m p e r a t u r e s so t h a t th e m e at
c o u ld b e s a n i t i z e d w ith t h e c h e m ic a l a g e n ts b e in g s t u d i e d t o d e te r m in e
w h e th e r s u c h a g e n ts w o uld b e e f f e c t i v e a t t h i s optim um te m p e r a t u r e r a n g e ,
B rew er c w , i n h i s w ork w ith t h e b a c t e r i a l c o n t e n t o f m a rk e t
m e a t s , c o n c lu d e d t h a t p r e p a r e d m e a ts u s u a l l y c o n t a i n e d more b a c t e r i a
t h a n f r e s h m e a t s , and t h a t o f t h e b a c t e r i a e n c o u n te r e d i n th e d i f f e r e n t
m e a ts t h e c o lo n g ro u p p r e d o m in a te d .

ia

.J e n s e n ( 14.8 ) m e n tio n e d t h a t c o l i f o r m o rg a n is m s a r e a b u n d a n t and
u b i q u i t o u s o n t h e k i l l i n g f l o o r , an d a lm o s t i n v a r i a b l y fo u n d o n t h e
s u r f a c e s o f t h e c a r c a s s e s w h ich a r e e x p o se d d u r i n g k i l l i n g f l o o r o p e r a ­
tio n s .
V o e g e li* s w ork (9 3 ) show ed t h a t t h e c u t t i n g u t e n s i l s w ere r e ­
s p o n s i b l e to a g r e a t e x t e n t i n , b a c t e r i a l c o n ta m in a ti o n o f p re p a c k a g e d
f r e s h m e a ts.
One c a n a s s o c i a t e th e f a c t s , t h e r e f o r e , t h a t c o l i f o r m o rg a n is m s
f o u n d o n t h e s u r f a c e o f c a r c a s s e s c a n c o n ta m in a te t h e c u t t i n g u t e n s i l s ,
w h ic h s u b s e q u e n tly s p r e a d t h e o rg a n is m s t o a l l c u t s o f m a rk e t m e a ts a s
fo u n d b y B rew er (I 4.) .

I n a d d itio n th e re i s th e p o s s i b i l i t y o f o th e r

s o u r c e s o f c o n ta m in a ti o n w i t h t h e s e o rg a n is m s s u c h a s th e h a n d s o f th e
h a n d le rs .
Waksman ( 91;) e x p e n s iv e ly re v ie w e d t h e a n t a g o n i s t i c r e l a t i o n b e ­
tw e e n m ic ro o rg a n is m s l i v i n g i n a s s o c i a t i o n i n c l u d i n g t h e tw o - s id e d
a n ta g o n is m e x i s t i n g b e tw e e n E s c h e r i c h i a c o l i an d c e r t a i n s a l m o n e l l a e .
H ow ever, s t r a i n s o f E . c o l i v a r i e d i n t h e i r i n h i b i t i v e p o w er a g a i n s t
s a lm o n e lla e w h ile s p e c i e s o f s a lm o n e lla e v a r i e d i n t h e i r r e s i s t a n c e to
in h ib itio n o f E. c o l i .
Two p u re c u l t u r e s o f E . c o l i w ere i s o l a t e d .
c a r c a s s a n d t h e o t j i e r fro m a human s t o o l .

One fro m a b e e f

B o th i n h i b i t e d S a lm o n e lla

c h o l e r a e s u i s v a r . k u n z e n d o r f and S a lm o n e lla e n t e r i t i d i s w hen grown i n
a s s o c i a t i o n w ith t h e s a lm o n e lla e ( 36 ) .

b2

T e s t organism s

Three s t r a i n s o f fo o d p o is o n in g S t a p h y lo c o c c u s , numbered 1 7 2 ,
1 7 8 , and 196 w ere u se d i n t h i s i n v e s t i g a t i o n .

The o r i g i n a l c u lt u r e s

had. b e e n o b ta in e d from D r. G. M. D ack, Food R esea rch I n s t i t u t e ,
U n i v e r s i t y o f C h icago .

The org a n ism s had b een p r e v io u s ly i s o l a t e d from

c h ip p e d b e e f and two d i f f e r e n t sam ples o f ham, and t h e i r t o x i c i t y had
b een p r o v e d s e v e r a l tim e s by th e u se o f m onkeys.
E ig h t s p e c ie s o f t e s t s a lm o n e lla e were o b ta in e d from th e s to c k
c u lt u r e s o f M ich igan S t a t e C o l l e g e .

The org a n ism s had b een o b serv ed to

p o s s e s s th e u s u a l c h a r a c t e r i s t i c s o f th e s p e c i e s .

The o rg a n ism s were

S a lm o n e lla c h o le r a e s u is ( v a r . R u n z e n d o r f), S a lm o n e lla p a r a t y p h i,
S a lm o n e lla e n t e r i t i d i s , S a lm o n e lla g a llin a r u n i, S a lm o n e lla s c h o t t m u l l e r i , ,
S a lm o n e lla typ him u riu m , S a lm o n e lla p u llo r u m , and S a lm o n e lla ty p h o s a .
S a lm o n e lla e are known to have c a u se d fo o d p o is o n in g o r r a th e r
fo o d i n f e c t i o n , a s i t m igh t be c a l l e d a c c o r d in g to p a t h o g e n e s is , o f d i s t i n c t
n a tu re.

B er g y * s Manual o f D e te r m in a tiv e B a c t e r io lo g y , 6th e d i t i o n , s t a t e s

t h a t o n ly f i v e s e r o ty p e s o f s a lm o n e lla e are o f s p e c i a l i n t e r e s t i n th e
f i e l d o f human m e d ic in e , nam ely S . p a r a ty p h i A , S . p a r a ty p h i B , S . para­
t y p h i C, and S . s e n d a i.

W h ile t h e s e organism s are human p a th o g e n s , th e

l i t e r a t u r e I s f u l l o f d e s c r ip t io n s o f fo o d p o is o n in g c a s e s ca u sed by
s a lm o n e lla e o f an im al o r i g i n , and more a t t e n t i o n i s b e in g g iv e n to them
a t p r e se n t.

S a n it a t io n a u t h o r i t i e s , f o r exam ple, a re m in d fu l o f th e

c o n t r o l o f r o d e n ts a s an Im p ortan t p h a se i n p r e v e n tin g fo o d p o is o n in g
from S . typ him u riu m .

h3

M ed ia u s e d
Due to th e la r g e numbers o f b a c t e r i a p r e s e n t on p i e c e s and c u t s
o f m eats r e s u l t i n g from h a n d lin g and coining i n c o n t a c t w ith v a r io u s ob­
j e c t s , i t becom es n e c e s s a r y , i n w orking w ith f r e s h m eats , to em ploy
m edia o f h ig h s e l e c t i v i t y i n o r d e r t h a t d i f f e r e n t i a l c o u n ts o f th e fo o d
p o is o n in g s t a p h y lo c o c c i and s a lm o n e lla e on them ca n be m ade.

M arket

m e a ts , o f c o u r s e , c o n ta in a p p r e c ia b le numbers o f org a n ism s (9 3 ) .

A

s e r i e s o f t r i a l s proved t h a t D ifc o Chapman-Stone medium, i s v e r y s u i t a b le
f o r d i f f e r e n t i a l c o u n tin g o f s t a p h y l o c o c c i , e s p e c i a l l y th e u s u a l fo o d
p o is o n in g t y p e , a lth o u g h o t h e r s o f t e n produ ce th e same Stone r e a c t i o n ,
a c l e a r h a lo around th e c o l o n i e s .

The s u r fa c e c o l o n i e s are d i s t i n c t and

s e p a r a t e when p l a t i n g i s p r o p e r ly c a r r ie d o u t .
S in c e th e S a lm o n e lla s p e c ie s u se d were fo u n d to grow on D ifc o
S a lm o n e lla S h i g e l l a Agar ( S . S . A g a r ), t h i s medium was v e r y s a t i s f a c t o r y
f o r d i f f e r e n t i a l c o u n ts a f t e r th e y had grown on th e m eat f o r a p e r io d
o f t im e .

The medium, e x e r t s d e la y in g and in h i b i t o r y e f f e c t s on o th e r

b a c t e r ia u s u a l l y p r e s e n t on th e m e a t, and a f t e r 1 2 - l l | h ou rs o f in c u b a tio n
a t 37 C s a lm o n e lla e appear i n g r a y is h o r p in k is h gray c o l o n i e s i f
b a c t e r i a l c o l o n i e s on th e p la t e a re n o t crow ded.

L a c to s e -fe r m e n te r s

appear i n b r ic k r e d c o l o n i e s .
E x p erim en ta l

Food p o is o n in g s t a p h y lo c o c c i and sa lm o n e lla e v a r ie d m arkedly i n
grow th when grown on p ie c e s o f raw b e e f and pork ta k e n from d i f f e r e n t

r e t a i l c u t s p r o b a b ly d u e to v a r i e d m o is tu r e c o n t e n t an d am ount o f n u t r i ­
ti v e m a te r ia ls on th e in o c u la te d

su rfa c e .

I n o r d e r t o o b t a i n c o m p a r a tiv e

c o u n ts i n p l a t i n g b lo c k s o f l e a n b e e f an d p o r k ,a b o u t 5> gram s w ere t a k e n
fro m t h e same r e t a i l c u t s and p r e p a r e d a s f o l l o w s s
( a ) L e a n p i e c e s o f ra w m e at c u t fro m 1 cm u n d e r t h e s u r f a c e
a s e p t i c a l l y w ere d e s i g n a t e d a s " d e e p l e a n m e at" .
(b ) L e a n p i e c e s o f raw m e at c u t from , t h e s u r f a c e o f r e t a i l c u t s ,
u s i n g s t e r i l e e q u ip m e n ts to a v o id f u r t h e r a d d i t i o n o f
b a c t e r i a , w e r e d e s i g n a t e d a s " a u t o c la v e d l e a n m e a t " .
( c ) L e a n p i e c e s o f m e a t c u t 1 cm b e n e a th t h e s u r f a c e and a u t o ­
c l a v e d a t l £ p o u n d p r e s s u r e f o r l £ m in u te s t o d e s t r o y a l l
s p o r e s p r e s e n t w ere d e s i g n a t e d a s " a u t o c l a v e d l e a n m e a t " .
To c o n s e r v e m o is tu r e d u r in g a u t o c l a v i n g e a c h p i e c e o f m e at
w as p l a c e d a t t h e ed g e o f t h e b o tto m o f a c l o s e d an d s l a n t e d
P e t r i d i s h ; t h e p i e c e o f m e at r e s t e d o n th e lo w e s t a n g le
fo rm ed b y t h e w a l l an d th e b o tto m o f th e P e t r i d i s h .
The

deep le a n

m e a t ( a ) , t h e s u r f a c e l e a n m eat ( b ) , and

th e a u to ­

c la v e d l e a n m e at ( c ) w e re i n o c u l a t e d w ith 2k h o u r n u t r i e n t b r o t h c u l t u r e s
o f t h e fo o d p o is o n in g o rg a n is m s an d l e f t c o v e r e d i n P e t r i d i s h e s a t
2 1 .1 - 2 6 .7 C (7 0 - 8 0 F ) f o r 2k h o u r s b e f o r e p l a t i n g i n o r d e r to com pare
t h e am ount o f g ro w th o n th e m .
To com pare t h e i n f l u e n c e o f te m p e r a tu r e ^ o th e r p i e c e s o f d e ep
l e a n m e a t,
ab o v e

ta k e n a t t h e same tim e

d e ep l e a n m e a t p i e c e s , w e re

fro m t h e same ch u n k o f m e at a s th e
a ls o p l a c e d i n P e t r i d i s h e s an d in o c u ­

l a t e d w i t h a l o o p f u l o f t h e r e s p e c t i v e f o o d p o is o n in g o r g a n is m s .

T hey

kS

w e re i n c u b a t e d f o r 2k h o u r s a t d i f f e r e n t te m p e r a t u r e r a n g e s b e f o r e p l a t ­
in g .

The a p p ro x im a te num ber o f t h e d i f f e r e n t o rg a n is m s i n a l o o p f u l

w ere d e te r m in e d b y p l a t i n g and a r e p r e s e n t e d i n , t a b l e s 3 a-nd U i n th e
f i r s t colum n d e s i g n a t e d w inoculum 11.

T h e se num bers w e re a l s o u s e d a s th e

s t a r t i n g p o i n t s i n p l o t t i n g t h e g ra p h s i n f i g u r e s 3 , U, 5 , an d 6 .
U n in o c u la te d p i e c e s o f m e at w e re u s e d a s c o n t r o l s an d w e re in c u b a t e d a t
t h e d i f f e r e n t te m p e r a t u r e r a n g e s f o r 2k h o u r s b e f o r e p l a t i n g f o r s ta p h y l o
c o c c i an d s a l m o n e l l a e .

C o n tr o l p i e c e s o f f r e s h d e e p l e a n m e at w ere a l s o

im m e d ia te ly p l a t e d t o d e te r m in e t o t a l num bers o f b a c t e r i a b y u s i n g
try p to n e -g lu c o s e -y e a s t-e x tra c t a g a r.
T e m p e ra tu re r a n g e s u s e d f o r i n c u b a t i n g th e d i f f e r e n t p i e c e s o f
m e a t w ere lu U - 1 0 .0 C (1(0-50 F ) , 1 0 . 0 - 1 5 . 6 C (5 0 -6 0 . F ) , 1 5 .6 - 2 1 .1 C
( 6 0 - 7 0 F ) , 2 1 .1 - 2 6 .7 C (7 0 -8 0 F ) , an d 2 6 .7 - 3 2 .2 C (8 0 -9 0 F ) .

I n each

c a s e m o is tu r e w as s u p p l i e d b y a b a s i n o f w a te r p l a c e d d i r e c t l y , b e lo w th e
c l o s e d P e t r i d i s h c o n t a i n i n g t h e i n o c u l a t e d m eat so t h a t e x c e s s i v e d e s s i c a t i o n w o u ld n o t ta k e p l a c e .
As w i l l b e shown l a t e r , t h e r e s u l t s o f th e e x p e r im e n ts i n d i c a t e d
t h a t fo o d p o is o n in g o rg a n is m s o n l e a n b e e f a n d p o rk d id n o t i n c r e a s e
i n num bers a t I4..U -IO .O C (1^0-50 F ) d u r in g 2k h o u r s b u t i n c r e a s e d m a rk e d ly
a t 2 1 .1 - 2 6 .7 C (7 0 -8 0 F ) and 2 6 .7 - 3 2 .2 C (8 0 -9 0 F ) .

An e x p e r im e n t to

d e te r m in e t h e g ro w th o f f o o d p o is o n in g o rg a n is m s on p o rk r i n d an d t h e
e x t e r n a l f a t o f t h e b e e f c a r c a s s w as a l s o c a r r i e d o u t b y u s i n g t h e ab o v e
te m p e r a t u r e r a n g e s f o r i n c u b a t i o n .

B lo c k s o f a b o u t 5 gram s o f l e a n p o r k

w ith t h e r i n d and b e e f w ith t h e e x t e r n a l f a t w ere c u t fro m t h e s u r f a c e .
E a c h o f t h e 2k h o u r b r o t h c u l t u r e s o f t h e o rg a n is m s u s e d was i n o c u l a t e d

U6

on th e p o rk r i n d and th e b e e f f a t .

A f te r th e in o c u la tio n th e in o c u la te d

m a t e r i a l s w e re i n c u b a t e d f o r 2k h o u r s a t t h e ab o v e t h r e e te m p e r a tu r e
ra n g e s b e fo re p l a t i n g .
The i n o c u l a t i o n i n a l l c a s e s w as done b y t o u c h in g a s p o t i n th e
c e n t e r o f t h e s u r f a c e o f t h e m e at t o b e i n o c u l a t e d w i t h a it mm w ir e
lo o p c o n t a i n i n g t h e b r o t h c u l t u r e o f t h e o rg a n is m u n t i l t h e c o n t e n t s
r a n down o n to t h e s p o t .

T h i s w as done to o b t a i n s i m i l a r , i n o c u l a t e d

a re a s.
I n i n o c u l a t i n g a l o o p f u l o f b r o t h c u l t u r e o n th e s u r f a c e o f p o rk
a n d /o r b e e f a s d e s c r i b e d above t h e r e was some d o u b t a s to w h e th e r th e
n u t r i e n t b r o t h m ig h t i n c r e a s e t h e n u t r i e n t s t h e r e o n r e s u l t i n g i n more
g ro w th t h a n t h e r e w o u ld b e w ith o u t t h e b r o t h .

To d e te r m in e t h e e f f e c t

o f t h e b r o t h o n t h e g ro w th o f t h e o r g a n is m s ,2 U h o u r b r o t h c u l t u r e s o f
t h e o rg a n is m s w ere c e n t r i f u g e d an d w ashed t h r e e tim e s w i t h p h y s i o l o g i c a l
T he f i n a l s u s p e n s io n s w ere a llo w e d to s e t t l e f o r 90 m in u te s

s a lin e .

u n t i l th e y a p p e a re d s i m i l a r i n c o n c e n t r a t i o n t o 2k h o u r b r o t h c u l t u r e s
w h ic h h ad n o t b e e n s h a k e n ; th e s u s p e n s io n s w e re th e n u s e d f o r i n o c u l a ­
tio n .

The r e s u l t s o f p l a t i n g fro m l e a n p o rk a n d b e e f , i n o c u l a t e d w ith

s u c h w ashed b a c t e r i a and in c u b a te d a t 2 6 .7 - 3 2 .2 C (8 0 -9 0 F ).,w e re e s s e n ­
t i a l l y t h e same a s w hen r e g u l a r 2h h o u r b r o t h c u l t u r e s w ere u s e d f o r
i n o c u l a t i o n ( l a s t c o lu m n s o f t a b l e s 3 and U) .
c lu d e d t h a t th e b r o t h h ad l i t t l e

I t w as, t h e r e f o r e , con­

o r no e f f e c t o n t h e g ro w th o f th e

b a c te ria .
The u s u a l p o u r p l a t e m eth o d o f p l a t i n g was fo u n d u n s a t i s f a c t o r y
when u s i n g C hapm an-S tone medium o r S . S . a g a r , e s p e c i a l l y i n

hi

d i f f e r e n t i a t i n g n um erous s p e c i e s o f b a c t e r i a on m e at i n th e S . S . a g a r .
The C h ap m an -S to n e medium w as n o t d e s ig n e d f o r m ak in g p o u r p l a t e s b e ­
c a u s e a f t e r r e h y d r a t i o n i t h a d a h e av y c o n s i s t e n c y a n d s o l i d i f i e d a t a
te m p e r a t u r e w e l l a b o v e 1+5 C .

S . S . a g a r d i d n o t show m ark ed d i f f e r e n c e s

b e tw e e n c o l o n i e s o f s a lm o n e lla e an d o t h e r o rg a n is m s fo u n d o n b e e f a n d
p o rk , i f

grow n u n d e r t h e s u r f a c e ; i t was q u i t e im p o s s i b le to d i f f e r e n t i a t e

t h e s e c o l o n i e s a f t e r 1 2 -1 6 h o u r i n c u b a t i o n an d a f t e r l o n g e r p e r i o d s o f
i n c u b a t i o n , 16-21+ h o u r s , th e medium was n o t i n h i b i t o r y an d a llo w e d g ro w th
o f num erous o r g a n is m s .
H ow ever, s u r f a c e c o l o n i e s o f s a lm o n e lla e on S . S . a g a r w ere
c h a r a c t e r i s t i c an d grew much l a r g e r t h a n c o l o n i e s o f o t h e r o rg a n is m s
a f t e r 11+-21 h o u r i n c u b a t i o n a t 37 C .

C o lo n ie s o f S ta p h y lo c o c c u s on th e

s u r f a c e o f C hapm an-S tone medium a l s o grew l a r g e r an d w ere m ore u n ifo rm
i n s i z e th a n s u b s u r f a c e c o l o n i e s .
A s u r f a c e p l a t i n g m ethod to a s s u r e d i f f e r e n t i a t i o n , s e p a r a t i o n ,
an d u n i f o r m i t y i n s i z e o f c o l o n i e s o f s ta p h y l o c o c c i an d s a lm o n e lla e was
d e v e lo p e d f o r more a c c u r a t e and e a s y c o u n tin g .

The m ethod i s a s f o l l o w s :

Chapm an-Stone medium and S . S . a g a r w ere p re p a re d as u s u a l and
p o u re d i n t o P e t r i d is h e s i n 2 5 -3 0 ml q u a n t i t i e s .

I t was n e c e s s a r y to

p o u r a l a r g e r volume th a n u s u a l i n th e P e t r i d is h b eca u se a f t e r s o l i d i ­
f i c a t i o n th e p l a t e was to be d r ie d a t 37 C f o r 2 h h o u rs and a t room,
te m p e ra tu re f o r a n o th e r i+8 h o u rs b e f o re u s e .
O n e -te n th m l. o f th e p r o p e r ly d i l u t e d m a te r ia l to be p l a t e d was
d e l i v e r e d from a 0 .1 ml s e r o l o g i c a l p i p e t t e on th e s u r f a c e o f a p re p a re d
agar p la te .

T h is inoculum was q u ic k ly s p re a d o v er th e s u r f a c e by means

ii-8

o f a s p re a d in g w ir e .

The s p r e a d i n g w ire w as made b y b e n d in g an o r d i n a r y

i n o c u l a t i n g n e e d le a t a 65 d e g r e e a n g le 170 mm fro m t h e h a n d le an d b e n d ­
i n g a g a i n arka70 d e g r e e a n g le 23 mm fro m t h e f i r s t b e n d a n d 7 ,5 mm fro m
t h e t i p ; i t was a w ir e b e n t tw ic e t o h a v e a 23 mm l e n g t h u s e d f o r s p r e a d ­
in g b e tw e e n t h e f i r s t b e n d an d t h e s e c o n d b e n d .

The t i p w a s , t h e r e f o r e ,

u p tu r n e d t o p r e v e n t d ig g in g i n t o t h e a g a r w h ile s p r e a d i n g .

The w ir e w as

fo u n d to g iv e m ore u n ifo rm r e s u l t s th a n t h e u s u a l g l a s s r o d u s e d f o r
s p re a d in g , p r o b a b ly b e c a u s e c o n s t a n t a m o u n ts o f in o c u lu m a d h e r e d t o th e
w ir e due to i t s

s m a ll d i a m e t e r .

F u r th e r m o r e , w i r e s w ere e a s y t o d u p l i ­

c a t e i n t h e s e d im e n s io n s and c o u ld b e c o n v e n i e n t l y s t e r i l i z e d i n th e
fla m e .
When t h e p l a t e c o n t a i n i n g t h e medium was p r o p e r l y d r i e d t h e s p r e a d ­
in g c o u ld b e done r a p i d l y b y r o t a t i n g t h e P e t r i d i s h i n th e l e f t h a n d
w h ile t h e r i g h t h a n d moved t h e s p r e a d in g w ir e t o an d f r o .

The m o is tu r e

o f t h e in o c u lu m w as a b s o r b e d i n a few s e c o n d s w h ich p r e v e n t e d t h e d e v e lo p ­
m ent o f s p r e a d in g c o l o n i e s .

A l l r e s u l t s c o u ld b e r e a d th e n e x t d a y a f t e r

p l a t i n g ( F i g . C - l , C - 2 , C - l a , an d C -2 a ) .
The sw a b in g m eth o d to rem ove b a c t e r i a fro m th e m eat ( 6 l ) a f t e r
r e p e a t e d t r i a l s showed w id e v a r i a t i o n s i n r e s u l t s .

T h is f a c t m ig h t b e

due to v a r i e d m o is tu r e c o n t e n t and a d h e s io n o f t h e b a c t e r i a o n th e s u r ­
f a c e o f t h e p o r k and b e e f e v e n o n d i f f e r e n t p a r t s - o f t h e same c u t s .

The

s u r f a c e o f p o r k and b e e f a l s o was i r r e g u l a r .
The i n o c u l a t e d and i n c u b a t e d p i e c e s o f l e a n p o r k and b e e f a n d / o r
t h e i r c o v e r in g s a s w e l l a s t h e c o n t r o l p i e c e s w ere d ro p p e d i n t o d i l u t i o n
b o t t l e s c o n t a i n i n g 10 to 100 ml o f d i s t i l l e d w a t e r .

The b o t t l e s w ere

s h a k e n 50 tim e s b e f o r e s u i t a b l e d i l u t i o n s w e re made fro m them and 0 .1 ml
q u a n t i t i e s w ere im m e d ia te ly p l a t e d i n d u p l i c a t e fro m e a c h d i l u t i o n .

F i g . C - l . P l a t e s made fro m th e same d i l u t i o n o f s ta p h y l o c o c c i
fo u n d on raw p o r k u s i n g C hapm an-S tone medium a f t e r 18 h o u r i n c u b a t i o n .
L e f t - c o l o n i e s o n s u r f a c e s p r e a d - p l a t e . R ig h t - r e g u l a r p o u r p l a t e
sh o w in g n e e d le p o i n t s u b s u r f a c e c o l o n i e s .

F i g . C - 2 . P l a t e s made fro m t h e same d i l u t i o n o f S a lm o n e lla
ty p h im u riu m r e c o v e r e d fro m raw p o rk u s i n g S . S . a g a r a f t e r 1 6 h o u r
i n c u b a t i o n . L e f t - s u r f a c e s p r e a d - p l a t e show ing r e d c o l o n i e s - c o l i f o r m s ; y e l l o w i s h g ra y c o l o n i e s - S a l m o n e lla . R ig h t - r e g u l a r p o u r
p l a t e sh o w in g p i n p o i n t s u b s u r f a c e c o l o n i e s j d a r k a r e a s - s u l f i t e
p r o d u c in g c o l o n i e s .

'-’0

F i g . C - l a . B la c k and w h ite s u p p le m e n t t o F i g . G - l show ing
c o Io ru .e s on s u r f a c e o f s p r e a d - p l a t e , l e f t and m in u te s u b s u r f a c e
c o l o n i e s on p o u r e d p l a t e , r i g h t .

F i g . C - 2 a . B la c k and w h ite s u p p le m e n t to F i g . C - 2 . L e f t p l a t e
shows s u r f a c e s p r e a d - p l a t e w i t h l a r g e d i s t i n c t c o l i f o r m and S a lm o n e lla
c o l o n i e s . The r i g h t p l a t e shows m in u te s u b s u r f a c e c o l o n i e s i n t h e
p oured p l a t e .

52

R e s u l t s and D is c u s s io n
As r e v ie w e d u n d e r th e t o p i c o f " g e n e r a l c o n s i d e r a t i o n " (p a g e 5 )

,

p o r k and b e e f w e re fo u n d to h ave r a t h e r l a r g e nu m b ers o f b a c t e r i a on
t h e s u r f a c e ( 8 9 ,3 8 ) .

H o w ev er, m o st o f t h e e a r l y w ork done on th e

b a c t e r i o l o g y o f t i s s u e s o f n o rm a l a n im a ls i n d i c a t e d t h a t m u s c le t i s s u e s
w e re s t e r i l e .

H a u s e r , N e i s s e r , O p i t z , M e s s n e r, Amako, W y ss o k o w its c h ,

T h o l e , H a s s , an d K u s te r a s c i t e d b y J e n s e n (U8) b e l i e v e d th e y w ere
s te rile .

R e c e n t l y G o ld b e rg e t a l . (3 5 ) s t u d i e d t h e i n h e r e n t m i c r o f l o r a

o f b e e f and d i f f e r e n t i a t e d 9h o rg a n is m s r e p r e s e n t i n g 12 g e n e r a i s o l a t e d
fro m th e d e ep t i s s u e s .
W h ile num bers o f b a c t e r i a on th e s u r f a c e o f p o rk an d b e e f may b e
l a r g e d e p e n d in g on t h e c o n ta m in a ti o n from c u t t i n g u t e n s i l s a s one o f t h e
c o n t r i b u t i n g f a c t o r s (9 3 ) , th e c o n t r o l p l a t i n g from f r e s h l e a n p o rk an d
b e e f , ta k e n 1 cm b e n e a th th e s u r f a c e , showed c o m p a r a tiv e ly v e ry s m a ll
c o u n ts r a n g in g fro m 3 to 60 p e r sq cm.

I t was e v id e n t t h a t th e c u t t i n g

u t e n s i l s , e v e n w hen s t e r i l e , m ig h t s t i l l c o n v ey some s u r f a c e b a c t e r i a
to t h e d e ep l e a n m e a t .
The d a t a p e r s e n t e d h e r e show no m arked d i f f e r e n c e s when p o is o n in g
s t a p h y l o c o c c i w e re grown a t 2 1 .1 - 2 6 .7 C (7 0 -8 0 F) on deep l e a n , a u t o ­
c l a v e d l e a n , a n d s u r f a c e l e a n p o rk an d b e e f .

L ik e w is e , s a lm o n e lla e d id

n o t v a r y s i g n i f i c a n t l y i n num bers when grown on f r e s h d eep l e a n m e a t
o r a u to c l a v e d d e ep l e a n m e at b u t showed a g r e a t r e d u c t i o n when grow n on
s u r f a c e l e a n p o rk and b e e f ( t a b l e s and f i g u r e s 1 an d 2 ) .

The r e d u c t i o n

I n t h e b a c t e r i a l c o u n ts o n s u r f a c e l e a n m eat may be a t t r i b u t e d

53

t o t h e a n ta g o n is m o f f e r e d b y o t h e r o rg a n is m s g ro w in g i n a s s o c i a t i o n
w i t h th e m , an d to l e s s a v a i l a b l e m o is tu r e b e c a u s e some d o u b t l e s s h ad
e v a p o ra te d .
The c o n t r o l p i e c e s o f deep l e a n p o rk and b e e f p l a c e d i n v a r i o u s
te m p e r a t u r e r a n g e s w ere b y no m eans s t e r i l e , ( t a b l e s 3 an d h) .

H o w ev er,

t h e i n i t i a l c o n ta m in a tio n o f t h e s e p i e c e s m ig h t nog h ave b e e n g r e a t
eno u g h to r e n d e r th e 'g ro w th o f s a lm o n e lla e s i g n i f i c a n t l y d i f f e r e n t fro m
t h a t on a u t o c l a v e d l e a n b e e f and p o r k .
F o o d p o is o n in g o rg a n is m s a p p e a re d to grow b e t t e r o n p o rk t h a n o n
b e e f e s p e c i a l l y a t 2 1 .1 - 2 6 .7 C (70 -8 0 F) and a ls o a t 2 6 .7 - 3 2 ,2 C (8 0 - 9 0 F) .
No m a rk e d i n c r e a s e i n num bers o f fo o d p o is o n in g s t a p h y l o c o c c i was o b ­
s e r v e d o n l e a n b e e f a t 1 0 .0 - 1 5 .6 C (5 0 -6 0 F ) d u r in g 2b h o u r s , b u t t h e
o rg a n is m s grew o n l e a n p o rk s t o r e d a t t h i s te m p e r a tu r e r a n g e , ( t a b l e s
and f i g u r e s 3 an d h) .
A t 1 0 .0 - 1 5 .6 C (5 0 -6 0 F) 2 o f t h e 8 s p e c i e s o f s a lm o n e lla e u s e d
i n c r e a s e d i n num bers on l e a n p o r k .w h ile 5 s p e c ie ^ d e c r e a s e d i n num bers
a n d 1 re m a in e d c o n s t a n t .

On l e a n b e e f a t t h i s te m p e r a tu r e r a n g e 2 o f

t h e 8 s p e c i e s o f th e s a lm o n e lla e i n c r e a s e d i n num bers w h ile 6 s p e c ie s
show ed d e c r e a s e s , ( t a b l e s 3 and U) .
w e re n o t so a c t i v e

T h is f a c t i n d i c a t e d t h a t s a lm o n e lla e

i n g ro w th an d r e p r o d u c t i o n a t t h i s te m p e r a tu r e ra n g e '

w i t h b e e f a n d p o r k a s th e m e d ia .
T e m p e ra tu re r a n g e s b e tw e e n 1 5 .6 - 3 2 .2 C (6 0 -9 0 F) w e re f a v o r a b l e
t o a l l t e s t o r g a n is m s , th e o p tim a l ra n g e b e in g 2 6 .7 - 3 2 .2 C
No i n c r e a s e o f th e

t e s t o rg a n is m s w as o b s e r v e d a t I4..I 1-IO .O

l e a n p o rk a n d b e e f , ( t a b l e s an d f i g u r e s 3 and h) .

(8 0 -9 0 F ) .
(1*0-50 F ) on

Sh

E x t e r n a l f a t o f t h e b e e f c a r c a s s a p p e a re d to b e r a t h e r inore f a v o r ­
a b l e to g ro w th o f f o o d p o is o n in g s t a p h y l o c o c c i t h a n p o rk r i n d .
S a lm o n e lla e , h o w e v e r, grew b e t t e r on t h e p o rk r i n d th a n o n th e e x t e r n a l
f a t o f t h e b e e f c a r c a s s , ( t a b l e s and f i g u r e s 5 &nd 6 ) .

T h e se c o v e r in g s

com pared w i t h th e l e a n m e a t, w ere p o o r m ed ia an d a llo w e d b u t l i t t l e
g ro w th o f t h e o rg a n is m s u s e d , ( t a b l e s 3 ,

$ an d 6) .

T h e se r e s u l t s i n ­

d i c a t e d t h a t th e n u t r i e n t s p r e s e n t on p o rk r i n d and e x t e r n a l f a t o f t h e
b e e f w ere l i m i t e d o r p o s s i b l y n o t so r e a d i l y a v a i l a b l e to t h e fo o d p o i s o n ­
in g b a c t e r i a .

T h e r e f o r e , p o rk an d b e e f s h o u ld b e k e p t an d h a n d le d w ith

s u c h n a t u r a l c o v e r in g s on w h en ev er p o s s i b l e .
A t 2 6 .7 - 3 2 .2 C (8 0 -9 0 F) t h e r e was g e n e r a l l y l e s s g ro w th o f fo o d
p o i s o n i n g o rg a n is m s o n p o rk r i n d an d e x t e r n a l f a t o n t h e b e e f th a n a t
2 1 .1 - 2 6 .7 C (7 0 -8 0 F ) , ( t a b l e s a n d f i g u r e s 9 an d 6 ) .
due to t h e e v a p o r a t i o n o f t h e s u r f a c e m o i s t u r e .

T h is was a p p a r e n t l y

T h e se c o v e r i n g s , o f

c o u r s e , c o n t a i n e d much l e s s m o is tu r e th a n l e a n m e a t.
Summary
1 . T h e re was no s i g n i f i c a n t d i f f e r e n c e s i n th e number o f fo o d p o is o n in g
s ta p h y l o c o c c i g ro w in g on raw f r e s h and co o k ed b e e f an d p o r k .
2 . S a lm o n e lla e d i d n o t d i f f e r s i g n i f i c a n t l y i n t h e i r g ro w th on t h e raw
f r e s h an d co o k ed l e a n b e e f a n d p o r k ta k e n fro m a 1 cm d e p th o f r e t a i l
c u ts .

T h ey grew much l e s s on th e s u r f a c e o f r e t a i l c u t s o f raw

b e e f a n d p o rk p r o b a b ly due to th e a n ta g o n is m o f f e r e d b y o t h e r o r g a n ­
is m s grow n i n a s s o c i a t i o n w i th them an d a l s o due t o d e s i c c a t i o n .

55

3 . P o rk i s a b e t t e r medium T o r g ro w th o f fo o d p o is o n in g s t a p h y l o c o c c i
and s a lm o n e lla e th a n b e e f ,
ll. The a tm o s p h e r ic te m p e r a tu r e r a n g e , e x c l u s i v e o f a v e r y h ig h ra n g e
s u c h a s 3 2 .2 - 3 7 .8 C (9 0 -1 0 0 F) o r a lo w r a n g e su c h a s f r e e z i n g ,
o p tim a l f o r g ro w th o f f o o d p o is o n i n g s t a p h y l o c o c c i and s a lm o n e lla e
on l e a n b e e f an d p o rk i s 2 6 .7 - 3 2 .2 C (8 0 -9 0 F) .

No g ro w th was o b ­

s e r v e d i n 2h h o u r s a t U .ii-1 0 .0 C (ioO-50 F) w h ich i s th e u s u a l
r e f r i g e r a t i n g zo n e o f h o u s e h o ld r e f r i g e r a t o r s .
5 . P o rk r i n d i s a b e t t e r medium o f g ro w th f o r f o o d p o is o n in g s t a p h y l o ­
c o c c i an d s a lm o n e lla e t h a n th e e x t e r n a l f a t o f th e b e e f c a r c a s s .
H ow ever, b o th th e r i n d and th e f a t a r e p o o r m ed ia com pared to th e
l e a n m e a t.

P o rk and b e e f , t h e r e f o r e , s h o u ld b e k e p t and h a n d le d w ith

t h e s e n a t u r a l c o v e r in g s on w h e n ev e r p o s s i b l e .

56

T a b le 1

■

G row th o f fo o d p o is o n in g o rg a n is m s o n b e e f a t 2 3 .9 t 2 .8 G
f o r 2h h o u r s . C o u n t i n m i l l i o n s
...
O rg an ism

In o cu lu m

Deep l e a n
beef

A u to c la v e d
le a n b eef

S u r fa c e
.le a n b e e f

S ta p h y lo c o c c u s 172

2 .000

2 , 500.000

3 , 700.000

l i , 500.000

S ta p h y lo c o c c u s 178

l.UOO

1 , 800.000

1 , 900.000

2 ,5 0 0 .000

S ta p h y lo c o c c u s 196

1 .900

2,100 .000

2 , 000.000

2 , 000.000

S a lm o n e lla c h o l e r a e s u i s
v a r . kunz e ndo r f

1 .700

260.000

2 U0 .000

230.000

S a lm o n e lla p a r a t y p h i

.060

2.200

3.000

.100

S a lm o n e lla e n t e r i t i d i s

.690

1.200

2.900

.800

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.i ;20

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S a lm o n e lla s c h o t t m u e l l e r i

.050

22.000

20 .000

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110 .000

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S a lm o n e lla p u llo r u m

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T a b le 2
G row th o f f o o d p o is o n in g o rg a n is m s on p o rk a t 2 3 . 9 - 2 . 8 C f o r
2i| h o u r s . C o u n t i n m i l l i o n s

O rg a n ism

In o cu lu m

Deep l e a n
p o rk

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l e a n p o rk

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l e a n p o rk

S ta p h y lo c o c c u s 1?2

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S ta p h y lo c o c c u s 178

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S ta p h y lo c o c c u s 196

1 .900

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3 ,3 0 0 .0 0 0

S a lm o n e lla c h o l e r a e s u i s
v a r . k u n z e n d o rf

1.700

1,U 00.000

1 ,7 0 0 .0 0 0

1 ,2 0 0 .0 0 0

S a lm o n e lla p a r a t y p h i

.060

U.500

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.690

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30.000

S a lm o n e lla g a llin a r u m

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150.000

200.000

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S a lm o n e lla s c h o t t m u e l l e r i

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80 .000

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1 ,9 0 0 .0 0 0

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70.000

S a lm o n e lla p u llo r u m

.230

670.000

330.000

100 .000

S a lm o n e lla ty p h o s a

.006

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6 .0 0 0

.020

S a lm o n e lla ty p h im u riu m

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66

PAKT I I .

EFFECT OF ORGANIC ACIDS AND CHLORAMPHENICOL IN SANITIZING
THE SURFACE OF BEEF AND PORK INOCULATED WITH
FOOD POISONING ORGANISMS
In tro d u c tio n

E x p e r im e n ta l r e s u l t s o b t a i n e d i n P a r t I showed t h a t t h e a tm o s p h e ric
te m p e r a t u r e r a n g e , e x c l u s i v e o f a v e r y h ig h ra n g e su c h a s 3 2 .2 - 3 7 .8 C
(9 0 -1 0 0 F ) o r a low te m p e r a tu r e ra n g e s u c h a s f r e e z i n g , o p tim a l f o r
g ro w th o f f o o d p o is o n in g s ta p h y l o c o c c i an d s a lm o n e lla e on l e a n p o rk an d
b e e f w as 2 6 .7 - 3 2 .2 C (8 0 -9 0 F) .

An e x p e rim e n t w a s, t h e r e f o r e , d e s ig n e d

to f i n d a c h e m ic a l a g e n t w hich w o u ld s a n i t i z e t h e s u r f a c e o f p o rk an d
b e e f i n o c u l a t e d w ith t h e f o o d p o i s o n in g o rg a n is m s and i n c u b a t e d a t t h i s
optim um te m p e r a tu r e r a n g e .

Such a c h e m ic a l a g e n t i n th e c o n c e n t r a t i o n

u s e d s h o u ld n o t be h a rm fu l to human b e i n g s , s h o u ld n o t m a rk e d ly a l t e r
t h e p h y s i c a l and c h e m ic a l p r o p e r t i e s o f th e s u r f a c e on th e t r e a t e d m e a t,
an d a b o v e a l l s h o u ld b e u n i v e r s a l l y a v a i l a b l e an d p r a c t i c a l to u s e .
E x p erim en ta l
As i n d i c a t e d o n p a g e 37 a c e t i c a c i d was l e t h a l to S ta p h y lo c o c c u s
a u r e u s a t O.Oli. p e r c e n t c o n c e n t r a t i o n an d to S a lm o n e lla a e r t r y c k e
( S a lm o n e lla ty p h im u riu m ) a t 0 .0 9 p e r c e n t (£ 7 ) .
D e h y d r o a e e tic a c i d i n h i b i t e d S . a u re u s a t 0 .3 p e r c e n t an d
S a lm o n e lla p u llo r u m a t 0 . 3 p e r c e n t ( 9 7 ) .

69

C h lo ra m p h e n ic o l ( C h lo ro m y c e tin ) i n h i b i t e d m o st s ta p h y l o c o c c i a t
5 .0 u g /m l a n d r e s i s t a n t s t r a i n s o f S a lm o n e lla ty p h o s a and S . ty p tiim u riu m
a t 5 .0 u g /m l (6 0 ) .
I n t h i s e x p e r im e n t c h lo r a m p h e n ic o l , sodium s a l t o f d e h y d r o a c e tic
a c i d , a c e t i c a c i d ( i n d i l u t e d 12 p e r c e n t o r 120 g r a i n v in e g a r ) , monoc h l o r a c e t i c a c i d , d i c h l o r a c e t i c a c i d , an d t r i c h l o r a c e t i c a c i d w ere t e s t e d
f o r t h e i r g e r m ic id a l e f f e c t s .
R e p e a te d t r i a l s w ith v a r io u s c o n c e n t r a t i o n s o f th e above o rg a n ic
a c i d s show ed t h a t th e s a n i t i z i n g e f f e c t o f th e a c i d s f o r t h e s u r f a c e o f
p o r k an d b e e f i n o c u l a t e d w ith th e f o o d p o is o n in g o rg a n is m s c o u ld b e d i s ­
t i n c t l y com pared a t 1 p e r c e n t c o n c e n t r a t i o n .

A lo w e r c o n c e n t r a t i o n th a n

t h i s a llo w e d to o much g ro w th and ab o v e 1 p e r c e n t t h e r e was i n s u f f i c i e n t
g ro w th f o r c o m p a r is o n , e s p e c i a l l y w i t h t h e s e a c i d s w h ich p ro v e d to be
e f f e c t i v e i n r e d u c in g t h e c o u n ts o f f o o d p o is o n in g o r g a n is m s .
C h lo ra m p h e n ic o l w as u s e d i n 10 u g /m l c o n c e n t r a t i o n w h ich was
d o u b le t h a t u s e d to i n h i b i t s a lm o n e lla e and m o st s ta p h y l o c o c c i (6 0 ) .
T h is c o n c e n t r a t i o n a l s o com pared f a v o r a b l y i n p r i c e w it h o t h e r c h e m ic a l
s o lu tio n s u sed .

F u r th e r m o r e , a h ig h c o n c e n t r a t i o n s u c h a s 25 u g /m l

im p a r te d some b i t t e r t a s t e t o t h e m e a t w h ich was t r e a t e d w it h th e s o l u ­
tio n .
B lo c k s o f d e ep l e a n p o rk and b e e f ( a b o u t 5 gram s) w ere i n o c u l a t e d
w ith 2h h o u r b r o t h c u l t u r e s o f th e f o o d p o is o n in g s t a p h y l o c o c c i a n d
s a lm o n e lla e a s d e s c r i b e d i n P a r t I .

A f t e r i n o c u l a t i o n th e p o rk and b e e f

w e re i n c u b a t e d a t 30 C (8 6 F ) f o r 90 m in u te s to a llo w th e e v a p o r a tio n
and a b s o r p t i o n o f th e m o is tu r e i n t h e in o c u lu m on t h e s u r f a c e o f th e m e a t.

70

T h i s tim e i n t e r v a l a ls o s im u la te d th e tim e e l a p s e d b e tw e e n th e k i l l i n g
a n d s t o r i n g o f p o r k and b e e f c a r c a s s e s i n th e c o o l e r .
A f t e r t h i s s h o r t p e r i o d o f i n c u b a t i o n o f th e i n o c u l a t e d p o rk an d
b e e f th e y w e re d ip p e d i n 1 p e r c e n t f r e s h l y p r e p a r e d a q u e o u s s o l u t i o n s
o f th e a c i d s u s e d an d 10 u g /m l c h lo r a m p h e n ic o l; e a c h p i e c e o f m e at was
d ip p e d i n a s e p a r a t e s t e r i l e b e a k e r c o n t a i n i n g th e s o l u t i o n , rem oved
im m e d ia te ly and p l a c e d i n a s e p a r a t e s t e r i l e P e t r i d i s h w h ic h was s l a n t e d
to p r o v id e d r a in a g e o f th e s o l u t i o n a d h e r in g to th e m e a t.
The P e t r i d i s h c o n t a i n i n g th e above i n o c u l a t e d an d t r e a t e d p ie c e
o f m e a t w as in c u b a t e d a g a in a t 30 G (8 6 F) f o r 22 1 /2 h o u rs th u s com­
p l e t i n g a 2l| h o u r i n c u b a t i o n p e r i o d fro m t h e tim e o f i n o c u l a t i o n .

A t th e

en d o f t h e i n c u b a t i o n p e r i o d t h e p ie c e o f m e at was d ro p p e d i n t o a
d i l u t i o n b o t t l e c o n t a i n i n g 10 to 100 m l o f d i s t i l l e d w a te r f o r t h e s u r ­
fa c e p l a t i n g p ro c e d u re a s d e s c rib e d i n P a r t I .
The r e s u l t s o f t h e s e e x p e r im e n ts showed t h a t 1 p e r c e n t a c e t i c a c i d
w as th e m o st e f f e c t i v e o f any o f t h e s o l u t i o n s u s e d i n r e d u c in g t h e number
o f b a c t e r i a b u t s t i l l p e r m i t t e d a c o n s i d e r a b l e num ber to g ro w .

For th is

r e a s o n 2 and U p e r c e n t s o l u t i o n s o f a c e t i c a c i d w ere t r i e d f o r s a n i t i z i n g
t h e m e a t.

The 1; p e r c e n t s o l u t i o n p ro v e d e f f e c t i v e a s shown i n t a b l e 9.

The s o u rc e o f t h e a c e t i c a c i d u s e d i n a l l e x p e r im e n ts was d i s t i l l e d
v in e g a r.
To d e te r m in e an y c h an g e i n f l a v o r due to h p e r c e n t v i n e g a r , s m a ll
and l a r g e r e t a i l c u t s o f p o rk a n d b e e f w ere d ip p e d i n t o i t and a llo w e d to
d r i p a t room te m p e r a t u r e , 2 1 .1 - 2 6 .7 C (7 0 -8 0 F) , f o r fro m 1 to 1; h o u rs
b e f o r e c o o k in g f o r c o n su m p tio n i n th e r e g u l a r m a n n e r.

71

A ls o to o b s e r v e p h y s i c a l c h a n g e s o n l a r g e r p i e c e s o f p o rk an d
b e e f t h a n th o s e u s e d f o r e x p e r im e n ta l w o rk , c h u n k s o f b e e f and p o rk
( a b o u t 30 to 100 g ram s) w e re d ip p e d i n 2b h o u r b r o t h c u l t u r e s o f t h e
fo o d p o is o n in g s t a p h y l o c o c c i an d s a l m o n e l l a e .

The i n o c u l a t e d p i e c e s o f

m e at w e re a llo w e d to d r i p a t room te m p e r a tu r e f o r 90 m in u te s b e f o r e
d ip p in g i n th e I4. p e r c e n t v i n e g a r .

T h ese p i e c e s o f m eat w ere n e x t

w ra p p ed i n p i e c e s o f m o is tu r e - v a p o r - p r o o f m e a t w ra p p in g p a p e r o r p l a c e d
i n c l o s e d P e t r i d i s h e s f o r o b s e r v a t i o n a f t e r s ta n d i n g 2b h o u rs a t room
te m p e ra tu re .

C o n t r o l p i e c e s w ere s i m i l a r l y i n o c u l a t e d a n d s t o r e d b u t

n o t t r e a t e d w ith t h e I4. p e r c e n t, v i n e g a r .
R e s u lts and D is c u s s io n
The s t r a i n s o f t h e f o o d p o is o n in g s t a p h y l o c o c c i u s e d i n t h e s e
e x p e r im e n ts w e re fo u n d t o be much m ore r e s i s t a n t to t h e o r g a n ic a c i d s
t e s t e d an d to c h lo r a m p h e n ic o l t h a n th e fo o d p o is o n in g s a lm o n e lla e
s t u d i e d , ( t a b l e s an d f i g u r e s 7 an d 8) .
When u s e d a s d ip p in g s o l u t i o n s f o r i n o c u l a t e d p o rk and b e e f
10 u g /m l c h lo r a m p h e n ic o l an d 1 p e r c e n t t r i c h l o r a c e t i c a c i d w ere fo u n d
t o s t i m u l a t e g row th o f th e fo o d p o is o n in g s ta p h y l o c o c c i i n s t e a d o f s u p ­
p r e s s i n g th e m , ( t a b l e s an d f i g u r e s 7 and 8) .

T h ese s o l u t i o n s i n t h e s e

c o n c e n t r a t i o n s w ere o b v io u s ly u s e l e s s f o r th e p u rp o s e o f s a n i t i z i n g m e a t .
The g e r m ic id a l e f f e c t o f th e a c i d s on th e fo o d p o is o n in g s t a p h y l o ­
c o c c i i n o c u l a t e d on th e s u r f a c e o f p o rk and b e e f was i n d e c r e a s i n g o r d e r :
a c e t i c , m o n o c h lo r a c e tic , d e h y d r o a c e tic (so d iu m s a l t )
The r e s u l t s a r e fo u n d i n t a b l e s an d f i g u r e s 7 and 8 .

and d i c h l o r a e e t i c .

72

O f "the 8 s p e c i e s o f s a lm o n e lla e u s e d S . c h o l e r a e s u i s v a r .
k u n z e n d o r f an d S . ty p h im u riu m i n o c u l a t e d o n l e a n p o rk a n d b e e f w ere m ore
r e s i s t a n t t h a n t h e o t h e r s to t h e g e r m ic id a l a c t i o n o f t h e a c id s an d
c h lo r a m p h e n ic o l.

The s a l m o n e l l a e , h o w e v e r, w ere n o t s t i m u l a t e d by

10 u g /m l c h lo r a m p h e n ic o l o r b y a 1 p e r c e n t c o n c e n t r a t i o n o f th e o r g a n ic
a c id s u s e d .

The g e r m ic id a l e f f e c t o f t h e v a r i o u s s o l u t i o n s on th e f o o d

p o i s o n i n g s a lm o n e lla e on th e p o r k and b e e f i n d e c r e a s i n g o r d e r w as:
a c e t i c , m o n o c h lo r a c e tic , d e h y d r o a c e tic (s o d iu m s a l t ) , d i h y d r o a c e t i c ,
t r i c h l o r a c e t i c a n d c h lo r a m p h e n i c o l .

T h is g e r m ic id a l e f f e c t on t h e

s a lm o n e lla e o f 10 u g /m l c h lo ra m p h e n ic o l an d o f 1 p e r c e n t t r i c h l o r a c e t i c
a c i d , h o w e v e r, d i d n o t d i f f e r v e r y m uch, ( t a b l e s an d f i g u r e s ? and 8) .
A c e t i c a c i d , t h e r e f o r e , was fo u n d to b e th e m o st e f f e c t i v e o f a l l
s o l u t i o n s t e s t e d i n r e d u c in g th e num bers o f f o o d p o is o n in g s t a p h y l o c o c c i
an d s a lm o n e lla e on th e s u r f a c e o f p o r k an d b e e f .

M o n o c h lo r a c e tic a c i d ,

w h ic h a l s o p r o v e d to be e f f e c t i v e , c a n n o t be l e g a l l y u s e d i n U n ite d
S ta te s .
F o u r p e r c e n t v in e g a r r e d u c e d t h e num bers o f th e fo o d p o is o n in g
s t a p h y l o c o c c i and s a lm o n e lla e m a r k e d ly .

S ev en o f th e 8 s p e c i e s o f

s a lm o n e lla e i n o c u l a t e d on t h e s u r f a c e o f l e a n p o rk gave z e ro c o u n ts when
it. p e r c e n t v in e g a r h a d been u s e d a s a d ip p in g s o l u t i o n .

The re m a rk a b le

g e r m ic id a l pow er o f a c e t i c a c i d i n t h i s r e s p e c t c a n b e f u r t h e r a p p r e c i ­
a t e d i f we c o n s id e r t h a t th e p o rk had b e e n i n o c u l a t e d w ith a v e ry h e a v y
in o c u lu m w h ic h w ou ld n o t u s u a l l y r e s u l t from n a t u r a l c o n ta m in a tio n ;
and t h a t t h e i n o c u l a t e d m eat h a d a l s o b e e n in c u b a t e d a t a v e r y f a v o r a b l e
te m p e r a tu r e .

I n s p i t e o f th e f a c t t h a t i n o c u l a t e d l e a n p o r k w hich h ad

' 73

n o t b e e n t r e a t e d w i t h a g e r m i c i d a l s o l u t i o n showed g r e a t e r am ount o f
g ro w th o f t h e fo o d p o is o n in g o rg a n is m s th a n s i m i l a r l y i n o c u l a t e d and
u n t r e a t e d l e a n b e e f 9 t h e num bers o f b a c t e r i a k i l l e d on th e p o rk a p p e a re d
g r e a t e r t h a n th o s e k i l l e d o n t h e b e e f due a p p a r e n t l y t o t h e g r e a t e r
r e t e n t i o n o f t h e ij. p e r c e n t v i n e g a r on l e a n p o r k th a n on l e a n b e e f 9
( t a b l e 9) .
When u s e d a s a d ip p i n g s o l u t i o n b p e r c e n t v in e g a r d i d n o t im p a r t
a n y a p p r e c i a b l e f l a v o r t o th e p o rk o r b e e f .

A lth o u g h a d i l u t e s o l u t i o n

o f v i n e g a r h a s b e e n u s e d a s a t e n d e r i z i n g a g e n t f o r some m e a ts (1 0 0 ) no
t e n d e r i z i n g e f f e c t w as n o te d when p o r k an d b e e f w h ic h h ad b e e n t r e a t e d
w i t h b p e r c e n t v i n e g a r w ere consum ed.
L a r g e r p i e c e s o f l e a n p o r k ( a b o u t 30 t o 100 gram s) w h ich h ad b e e n
d ip p e d i n I4. p e r c e n t v in e g a r h ad a s l i g h t l y w h i t e r s u r f a c e th a n n o rm al
a f t e r few h o u r s .

The l a r g e r p i e c e s o f l e a n b e e f d ip p e d i n t h e same

s o l u t i o n a l s o a p p e a re d w h i t e r t h a n n o rm a l u n l e s s t h e y w e re w rap p ed i n
a i r t i g h t m a t e r i a l o r w here t h e t r e a t e d s u r f a c e l a y f l a t a g a i n s t th e
b o tto m o f a P e t r i d i s h i n w h ich c a s e t h i s p o r t i o n r e t a i n e d i t s n a t u r a l
c o l o r ; t h e s u r f a c e e x p o se d to t h e a i r i n t h e P e t r i d i s h becam e w h i t e r
t h a n n o rm a l.
T h is c h a n g e i n c o l o r a l s o o c c u r r e d i n t h e l a r g e r p i e c e s o f p o rk
and b e e f i n o c u l a t e d w ith t h e f o o d p o is o n i n g s t a p h y l o c o c c i and s a l m o n e l l a e .
L a r g e r p i e c e s o f b e e f w h ich h ad b e e n i n o c u l a t e d w ith t h e fo o d p o is o n in g
o rg a n is m s b u t n o t t r e a t e d w i t h U p e r c e n t v in e g a r g ave o f f o f f e n s i v e
o d o r s an d d a rk e n e d o n t h e s u r f a c e a f t e r 2b h o u rs s t a n d i n g a t room te m p e ra ­
tu re .

T hose p i e c e s s i m i l a r l y i n o c u l a t e d b u t t r e a t e d w i th t h e v i n e g a r

7h

re m a in e d a lm o s t n o rm a l i n o d o r a n d c o l o r ; t h e c o l o r a s j u s t m e n tio n e d
a p p e a re d n o rm a l o n t h e s u r f a c e com ing i n c o n t a c t w ith a n a i r t i g h t w ra p ­
p in g m a t e r i a l o r t h e b o tto m o f a P e t r i d i s h , ( f i g . C -3 ) .
B o th th e i n o c u l a t e d an d u n in o c u la t e d l e a n p o r k w h e th e r t r e a t e d
o r n o t w i t h U p e r c e n t v i n e g a r , e m i tte d a f o u l o d o r an d p r e s e n t e d an
unw holesom e a p p e a r a n c e a f t e r 2 b h o u rs s t a n d i n g a t room t e m p e r a t u r e .

Summary
1 . T he fo o d p o i s o n i n g s t a p h y l o c o c c i u s e d i n t h e s e e x p e r im e n ts w ere more
r e s i s t a n t t h a n t h e s a lm o n e lla e t o t h e g e r m ic id a l a c t i o n o f d i c h l o r a c e t i c a c i d , d e h y d r o a c e tic a c i d (s o d iu m s a l t ) , m o n o c h lo r a c e tic a c i d ,
and a c e t i c a c i d .
2 . A c h lo r a m p h e n ic o l s o l u t i o n o f 10 u g /m l and a 1 p e r c e n t s o l u t i o n o f
t r i c h l o r a c e t i c a c i d w ere fo u n d to s t i m u l a t e g ro w th o f th e fo o d p o is o n ­
i n g s t a p h y l o c o c c i when u s e d a s d ip p in g s o l u t i o n s i n a n a tt e m p t to
s a n i t i z e t h e i n o c u l a t e d s u r f a c e o f p o rk and b e e f .
3 . When u s e d f o r s a n i t i z i n g t h e s u r f a c e o f th e i n o c u l a t e d p o r k an d b e e f ,
t h e g e r m ic id a l e f f e c t on f o o d p o is o n i n g s a lm o n e lla e o f th e 1 p e r c e n t
o r g a n ic a c i d s o l u t i o n s an d o f 10 u g /m l c h lo ra m p h e n ic o l was i n d e c r e a s ­
in g o r d e r ;

a c e tic ,

m o n o c h lo r a c e tic ,

d e h y d r o a c e tic (so d iu m s a l t ) ,

d i h y d r o a c e t i c , t r i e h l b r a e e t i e a n d .c h lo r a m p h e n ic o l.

The g e r m i c id a l

e f f e c t on s a lm o n e lla e o f 1 p e r c e n t t r i c h l o r a c e t i c a c i d and o f 10
u g /m l c h lo r a m p h e n ic o l, h o w e v e r, was a b o u t t h e sam e.
ij.. The above d e c r e a s i n g o r d e r o f g e r m ic id a l e f f e c t a l s o a p p l i e d to th e
f o o d p o is o n in g s t a p h y l o c o c c i w h ich h a d b e e n i n o c u l a t e d on p o r k and

75

b e e f e x c e p t t h a t 1 p e r c e n t t r i c h l o r a c e t i c a c i d and 10 u g /m l c h l o r ­
a m p h e n ic o l s t i m u l a t e d t h e i r g ro w th .
5.

A c e tic a c i d w as

fo u n d t o b e t h e

to s a n i t i z e t h e i n o c u l a t e d l e a n p o r k
*

'

m o st e f f e c t i v e o f a l l t h e a g e n ts u s e d
an d b e e f .

F our p e r c e n t v in e g a r

*

w as fo u n d t o b e a n e f f e c t i v e a n d p r a c t i c a l d ip p in g s o l u t i o n to
d e s t r o y t h e f o o d p o is o n in g s ta p h y l o c o c c i and s a lm o n e lla e o n th e s u r ­
fa c e o f p o rk and b e e f .
6 . I f t h e b e e f vwas^ w rap p ed i n a i r t i g h t m a t e r i a l a f t e r d ip p in g i n U p e r
c e n t v in e g a r t h e r e was no ch an g e o f c o l o r due to t h i s t r e a t m e n t .
F u r th e r m o r e , t h e t r e a t e d b e e f k e p t lo n g e r due to d e s t r u c t i o n o f m ic ro ­
o rg a n is m s fo u n d o n t h e s u r f a c e .
7.

The d e s t r u c t i o n

o f t h e f o o d p o is o n in g s ta p h y l o c o c c i an d s a lm o n e lla e

on t h e s u r f a c e o f p o r k b y h p e r c e n t v i n e g a r a p p e a re d g r e a t e r th a n
t h a t o n b e e f due a p p a r e n t l y t o g r e a t e r r e t e n t i o n o f t h e v in e g a r on
p o rk .

F o rk t r e a t e d ' w ith h p e r c e n t v i n e g a r becam e w h i t e r on th e s u r ­

f a c e th a n n o rm a l.

«

8 . F o u r p e r c e n t v i n e g a r d i d n o t im p a r t an y a p p r e c i a b l e f l a v o r to t h e
p o rk an d b e e f w h ic h h ad b e e n d ip p e d i n i t .

F i g . C -3 . Two p ie c e s of b e e f removed from the same c u t and
i n o c u la te d w ith Salm onella e n t e r i t i d i s . The photographed
s u r f a c e s had been kept i n c o n ta c t w ith th e bottoms o f P e t r i
d is h e s .
L e f t - c o n tr o l
R ig h t - t r e a t e d w ith U p e r c e n t v in e g a r

77

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62

GENERAL DISCUSSION
The r e s u l t s , -o f t h e s tu d y o n t h e g ro w th o f fo o d p o i s o n in g s t a p h y l o ­
c o c c i an d s a lm o n e lla e o n th e s u r f a c e o f raw l e a n p o r k and b e e f showed
t h a t t h e s e m e a ts w ere f a v o r a b l e m e d ia f o r t h e g ro w th o f th e o rg a n is m s .
A t a room te m p e r a tu r e o f 2 1 .1 - 2 6 .7 C (7 0 -8 0 F ) and a t 2 6 .7 - 3 2 .2 C (8 0 -9 0 F)
t h e s e o rg a n is m s i n c r e a s e d t o l a r g e num bers o n t h e s u r f a c e o f l e a n p o rk
and b e e f d u r in g 2k h o u r s y ( t a b l e s 3 and W .

The s u r f a c e m o is tu r e o f t h e

m e a ts an d t h e h u m id ity o f th e a i r a l s o d e te r m in e d th e b a c t e r i a l g ro w th to
a g r e a t e x t e n t ; i f th e s u r f a c e o f l e a n p o r k and b e e f was

d r i e r th a n

n o rm a l due t o a h ig h te m p e r a tu r e o f 2 6 .7 - 3 2 .2 C (8 0 -9 0 F ) t o g e t h e r w ith
a lo w h u m id ity t h e g ro w th w o u ld b e l e s s th a n a t a n e v e n lo w e r te m p e r a tu r e
o f 2 1 .1 - 2 6 .7 C (7 0 - 8 0 F ) t o g e t h e r w ith a h ig h h u m id ity .

A re frig e ra tin g

t e m p e r a tu r e o f l|..lj.-10.0 C (IjO-^O F ) w as e f f e c t i v e i n p r e v e n t i n g th e
g ro w th o f f o o d p o is o n in g s ta p h y l o c o c c i and s a lm o n e lla e o n t h e s u r f a c e o f
l e a n p o rk a n d b e e f f o r a t l e a s t 2k h o u r s . A lso ,, e n t e r o t o x i n was n o t p r o ­
d u c e d b y f o o d p o is o n in g s ta p h y l o c o c c i a t t h i s t e m p e r a t u r e .
To d e te r m in e t h e num bers o f b a c t e r i a on th e s u r f a c e o f raw p o r k
and b e e f .was a d i f f i c u l t p ro b le m .

A sw ab b in g m ethod ,u sed b y M allm ann and

C h u r c h i l l ( 6 l ) t o rem ove b a c t e r i a fro m a f o u r - i n c h s q u a r e a r e a o n t h e
s u r f a c e o f th e b e e f q u a r t e r w i th a s t e r i l e m o is t c o t t o n sw ab5showed v e r y
m ark ed v a r i a t i o n s i n b a c t e r i a l c o u n t s .

The a u th o r s s t a t e d t h a t t h i s

v a r i a t i o n was due to t h e i r r e g u l a r i t y i n t h e c o n ta m in a tio n o f t h e c a r c a s s
an d v a r i a b i l i t y i n - c o n t a m i n a t i o n o f t h e v a r i o u s c a r c a s s e s .

They b e l i e v e d

63

t h a t t h e m ethod u n d o u b te d ly f a i l e d to rem ove a l l t h e o rg a n is m s b u t i t
gave c o m p a ra b le r e s u l t s , was s im p le and in v o lv e d l e s s l a b o r an d e q u ip m e n t.
W h ile t h e above sw ab b in g m ethod may b e w e l l a p p l i e d f o r an i n v e s t i ­
g a t i o n w h ich r e q u i r e s o n l y a p p ro x im a te num bers o f b a c t e r i a i t was fo u n d
u n s a t i s f a c t o r y f o r a c o m p a riso n o f th e g ro w th o f f o o d p o is o n in g s ta p h y l o ­
c o c c i and s a lm o n e lla e o n th e s u r f a c e o f l e a n p o rk an d b e e f a t v a r io u s
te m p e r a tu r e r a n g e s and f o r c o m p a riso n of- th e g e r m ic id a l e f f e c t o f some
o r g a n ic a c i d s an d c h lo ra m p h e n ic o l on t h e gro w th o f t h e s e o rg a n is m s on
l e a n p o r k and b e e f .

V a r i a b i l i t y i n t h e s u r f a c e m o is tu r e and a d h e s iv e n e s s

o n d i f f e r e n t p a r t s o f t h e p o rk and b e e f c a r c a s s e s a n d ev en on t h e same
c u t s c o n t r i b u t e d to th e v a r i a t i o n i n num bers o f b a c t e r i a w h ich w ere
o b t a i n e d b y t h e sw abbing m e th o d .

F u r th e r m o r e , t h e s u r f a c e s o f p o rk an d

b e e f w ere i r r e g u l a r .
To r e c o v e r t h e o rg a n is m s w h ic h h a d b e e n i n o c u l a t e d o n th e s u r f a c e
o f raw l e a n p o rk a n d b e e f and t h e i r c o v e r in g s f o r p l a t i n g a f t e r 2 U -hour
i n c u b a t i o n , i t was fo u n d t h a t t h e r e was l e s s v a r i a t i o n i n num bers o f
b a c t e r i a w hen th e i n o c u l a t e d p i e c e s o f p o rk and b e e f w ere sh a k e n i n th e
d e s i r e d d i l u t i o n o f d i s t i l l e d w a te r i n d i l u t i o n b o t t l e s to rem ove th e
b a c te ria .
P o rk r i n d an d e x t e r n a l f a t o f th e b e e f c a r c a s s w ere p o o r m ed ia
f o r t h e g ro w th o f f o o d p o is o n in g s t a p h y l o c o c c i and s a lm o n e lla e i n com­
p a r i s o n to th e l e a n p o rk an d b e e f , ( t a b l e s 5> and 6) .
To d e te r m in e t h e num ber o f s a lm o n e lla e w h ich h a d b e e n i n o c u l a t e d
o n raw p o r k an d b e e f a f t e r 2b h o u r i n c u b a t i o n was a n o th e r a i f f i c u l t
p ro b le m due to t h e p r e s e n c e o f o t h e r o rg a n ism s on th e m e a ts .

S e g a lo v e

a n d D ack (8 0 ) , when th e y s t u d i e d t h e g ro w th o f b a c t e r i a a s s o c i a t e d w ith
fo o d p o i s o n i n g , e x p e r i m e n t a l l y i n o c u l a t e d i n t o d e h y d r a te d m e a ts , a u t o c la v e d a l l t h e i r d e h y d r a te d p o rk a n d b e e f sa m p le s i n a i r t i g h t c o n t a i n e r s
b e f o r e i n o c u l a t i n g w ith s a l m o n e l l a e .

T h is h e a t tr e a t m e n t d o u b tl e s s

a l t e r e d t h e c h e m ic a l c o m p o s itio n o f th e o r i g i n a l m a t e r i a l s a s w e l l a s
d e s t r o y e d a l l m ic ro o rg a n is m s p r e s e n t on th em ; b o th o f t h e s e f a c t o r s
m ig h t i n f l u e n c e th e g ro w th o f t h e i n o c u l a t e d b a c t e r i a .

H ow ever, th e y

w o rk ed w i t h p o rk a n d b e e f w h ic h had b e e n d e h y d r a te d and a l s o s a l t e d ,
t h e r e f o r e , th e c o m p o s itio n o f s u c h m e a ts a p p ro a c h e d t h a t o f cooked m e a ts
i n c o m p a ris o n w ith t h e u n s a l t e d f r e s h m a rk e t m e a ts .

The o r i g i n a l b a c t e r i ­

a l l o a d o f su ch d e h y d r a te d and s a l t e d m e a ts was a ls o lo w e r th a n t h a t o f
f r e s h m a rk e t m e a t s .
The r e s u l t s o f th e e x p e r im e n ts i n t h e p r e s e n t s tu d y showed t h a t
t h e r e was no s i g n i f i c a n t d i f f e r e n c e b e tw ee n th e g ro w th o f fo o d p o is o n in g
s t a p h y l o c o c c i and s a lm o n e lla e on raw l e a n p o rk an d b e e f ta k e n 1 cm b e n e a th
t h e s u r f a c e and o n c o o k ed l e a n p o rk and b e e f when in c u b a te d a t 2 1 .1 - 2 6 .7 C
(7 0 -8 0 F) .

H ow ever, t h e r e was l e s s g ro w th o f s a lm o n e lla e i n o c u l a t e d on

t h e s u r f a c e l e a n p o rk an d b e e f ta k e n fro m t h e r e g u l a r r e t a i l c u t s due to
t h e a n ta g o n is m o f f e r e d b y o t h e r o rg a n is m s p r e s e n t , e s p e c i a l l y

E. c o li,

and to t h e e v a p o r a t i o n o f s u r f a c e m o i s t u r e .
S in c e t h e s tu d y was to d e te rm in e th e g ro w th o f fo o d p o is o n in g
s t a p h y l o c o c c i a n d s a lm o n e lla e o n raw p o rk an d b e e f a t v a r io u s te m p e r a tu r e
r a n g e s a n d a ls o t o c o n t r o l t h e o rg a n is m s o n

raw

p o rk and b e e f by

o f c h e m ic a l a g e n ts a l l m e at sa m p le s u s e d i n

th e

e x p e rim e n ts w ere n o t

a u to c la v e d .

th e u s e

65

S.

S . a g a r w h ic h p ro v e d to be e x c e l l e n t i n d i f f e r e n t i a t i n g

c o l o n i e s o f s a lm o n e lla e from o t h e r o rg a n is m s b y th e s t r e a k e d p l a t e was
fo u n d t o b e u n s a t i s f a c t o r y f o r m ak in g th e r e g u l a r p o u re d p l a t e f o r
b a c t e r i a l c o u n t a s f a r a s th e d i f f e r e n t i a t i o n w as c o n c e rn e d .

S in c e t h e

u s u a l s t r e a k e d p l a t e m e th o d c o u ld n o t be u s e d f o r c o u n tin g b a c t e r i a
a s u r f a c e p l a t i n g m ethod was d e v e lo p e d to a s s u r e d i f f e r e n t i a t i o n ,
s e p a r a t i o n , an d u n i f o r m i t y i n s i z e o f c o lo n i e s o f s a lm o n e lla e on S . S .
a g ar.

C hapm an-S tone medium was s i m i l a r l y u s e d a s a s e l e c t i v e medium

w h ic h p e r m i t t e d c o u n tin g o f s ta p h y lo c o c c u s c o l o n i e s w ith g r a t i f y i n g
re s u lts .
P o rk was fo u n d to be a b e t t e r medium f o r th e fo o d p o is o n in g o rg a n ­
ism s th a n b e e f .

F o o d p o is o n in g s ta p h y l o c o c c i e x c e e d e d s a lm o n e lla e i n

g ro w th on l e a n p o r k and b e e f and t h e i r c o v e r in g s an d a ls o e x ce e d them i n
t h e i r r e s i s t a n c e to th e o r g a n ic a c i d s t e s t e d and t o c h lo r a m p h e n ic o l.
A t 1 p e r c e n t c o n c e n t r a t i o n a c e t i c a c i d was fo u n d more e f f e c t i v e
t h a n m o n o c h lo r a c e tic a c i d , d e h y d r o a c e tic a c i d (s o d iu m s a l t ) , d i c h l o r a c e t i c
a c i d , and t r i c h l o r a c e t i c a c i d i n d e s t r o y i n g th e fo o d p o is o n in g o rg a n ism s
o n p o rk an d b e e f .

The 1 p e r c e n t s o l u t i o n o f a c e t i c a c id was a ls o m ore

e f f e c t i v e th a n 10 u g /m l c h lo ra m p h e n ic o l i n t h i s r e s p e c t .

C o n s id e r a b le

num bers o f o r g a n is m s , h o w e v e r, re m a in e d v i a b le a f t e r t r e a t m e n t w ith 1
p e r cen t a c e tic a c id .
F o u r p e r c e n t v in e g a r was much m ore e f f e c t i v e th a n 1 p e r c e n t
a c e t i c a c i d i n d e s t r o y i n g t h e f o o d p o is o n in g o rg a n is m s i n o c u l a t e d on p o rk
an d b e e f .
and b e e f .

The s o l u t i o n d id n o t im p a r t any a p p r e c ia b le f l a v o r to th e p o rk

B e e f t r e a t e d w i t h I4 p e r c e n t v in e g a r r e t a i n e d th e n a t u r a l c o l o r
l o n g e r an d k e p t l o n g e r i f w rapped i n a i r t i g h t m a t e r i a l due to d e s t r u c t i o n
o f many m ic ro o rg a n is m s fo u n d on t h e s u r f a c e .

87

GENERAL CONCLUSION

0
P o r k an d b e e f a r e good m e d ia f o r f o o d p o is o n in g s t a p h y l o c o c c i
an d s a lm o n e lla e w h ic h i n c r e a s e d to g r e a t num bers a t 1 5 .6 - 3 2 .2 G
( 6 0 - 9 0 F ) i n 2k h o u r s ,
A r e f r i g e r a t i n g te m p e r a tu r e o f U .U -1 0 .0 C (1*0-50 F) i n th e h o u s e ­
h o ld r e f r i g e r a t o r B ffe e .tiy fe ly is u p p re s ;s e s rs t h e g ro w th o f th e fo o d p o is o n ­
i n g o rg a n is m s f o r a t l e a s t 2k h o u r s .
W h en ev er p o s s i b l e p o rk s h o u ld b e k e p t an d h a n d le d w ith th e r i n d
an d b e e f w i t h t h e e x t e r n a l f a t o f t h e b e e f c a r c a s s i n t a c t b e c a u s e t h e s e
n a t u r a l c o v e r in g s a r e p o o r m e d ia f o r th e g ro w th o f t h e f o o d p o is o n in g
s t a p h y l o c o c c i an d s a l m o n e l l a e .
F r e s h p o r k an d b e e f s h o u ld b e d ip p e d i n f o u r p e r c e n t v in e g a r
b e f o r e k e e p in g i n a c o ld s t o r a g e o r d i s p l a y i n g f o r s a l e .

T h is tr e a tm e n t

i s p r a c t i c a l a n d e f f e c t i v e i n d e s t r o y i n g th e fo o d p o is o n in g s ta p h y l o c o c c i
a n d s a lm o n e lla e t h a t may c o n ta m in a te t h e s u r f a c e o f t h e m e a ts .
v i n e g a r d o e s n o t im p a r t an y a p p r e c ia b le f l a v o r t o th e m e a t s .

The

88

LITERATURE CITED
1 . B a r b e r , M. A .^ M ilk p o is o n in g due to a ty p e o f S ta p h y lo c o c c u s a l b u s
o c c u r r i n g i n th e u d d e r o f a h e a l t h y cow . P h i l i p p i n e J . S c i . ,
9 , 5 1 5 -1 9 , 1 9 1 h .
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S ta p h y lo c o c c u s e n t e r o t o x i n . J . E x p t l . M e d ., 7 2 , 669-8!*, 191*0.
3 . B o r n s t e i n , S . a n d S a p h a , J . Fow l S a lm o n e lla p a th o g e n ic f o r m an.
J . I n f e c t . D i s . , 7 1 , 5 5 , 19T+21
1*. B re w e r, C . M. T h e 'B a c te r io lo g y o f m a rk e t m e a ts .
51*3-60, 1 9 2 5 .

J . o f B a c t., 1$,

5 . C a r t e r , M. J . , P o w e ll, M. P . , and B o r t s , I . H . S a lm o n e lla i n h e n
e g g s . P u b . H e a lth R e p ., 2l*, 7 7 8 -8 1 , 1 9 5 0 .
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i n f o o d s . I I I . E f f e c t o f c h o c o l a te and c o c o a f i l l i n g s on
i n h i b i t i n g g ro w th o f s t a p h y l o c o c c i . Food R e s . , 7 , 9 6 - 9 , 191*2.
7 . _________ ____________ . IV . E f f e c t o f c o o k in g b a k e r y c u s t a r d s .
R e s . , 7 , 1 0 0 -0 3 , 191*2.

Food

8 . C a t h c a r t , i f . H ., G o d k in , W . J . , and B a r n e t t , G. Growth o f S ta p h y lo c o c c u s a u r e u s i n v a r i o u s p a s t r y f i l l i n g s . Food R e s . , 1 2 ,
iu 2 - 5 o ,T 9 ir r r
9 . C h e r r y , W. B . , S c h e r a g o , M ., an d W eav er, R . H . The o c c u r r e n c e o f
S a lm o n e lla i n r e t a i l m e at p r o d u c t s . Am. J . H y g ., 3 7 , 2 1 1 -1 5 ,
1953 T
1 0 . C la r e n b u r g , A . , an d B u r g e r , H . C . S u r v iv a l o f S a lm o n e lla i n b o i l e d
d u ck s* e g g s . F ood R e s . , 1 5 , 31*0-1*1, 1 9 5 0 .
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1 2 . C row e, M. A l o c a l i z e d o u tb r e a k o f S a lm o n e lla fo o d p o i s o n in g a p p a r ­
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S ta p h y lo c o c c u s . J . P r e v . M ed. h , 1 6 7 -7 5 , 1 9 3 0 .

89

I k . D a c k , G. M ., J o r d o n , E . 0 . , and W o o lp e r t, 0 . C . A tte m p ts to
im m unize human v o l u n t e e r s w i t h s ta p h y l o c o c c a l f i l t r a t e s t h a t
a r e t o x i c t o man when s w a llo w e d . J . P r e v . M e d .. 5 l£ L -5 9
1931.
'
*
5
1 5 . D a ck , G. M. S ta p h y lo c o c c i i n r e l a t i o n to fo o d p o i s o n i n g .
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Am. J .

16 • ____________. S ta p h y lo c o c c u s f o o d p o is o n in g - s t i l l a s e r i o u s
p ro b le m . F o o d I n d s . , 1 8 , 1 8 6 8 -6 9 , 1 9 9 2 , 19U 6.
1 7 . ____________. B a c t e r i a l fo o d p o is o n in g s and t h e i r im p o rta n c e i n t h e
b a k in g i n d u s t r y . B a k e r* s d ig e s t.^ 2 1 , 1 2 6 -2 7 , 19U7.
1 8 . ____________. F ood p o i s o n i n g .
C h ic a g o , 1 1 1 ., 19l±9.

The U n i v e r s i t y o f C h icag o P r e s s ,

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. B . E x p e rim e n ts w ith S ta p h y lo c o c c u s
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2 3 - 6 , 19U 6.

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S a lm o n e lla
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An outbreak
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'
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A

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B a c t.

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