is usually low among others. Foods most
associated with shigellosis are those subjected
to a large amount of handling or those con-
taminated with waterborne Shigella. Foods
most likely to be infected with this microor-
ganism are potato, chicken, shrimp and tuna
salads, and seafood/shellfish. Most of the
outbreaks have occurred in foodservice estab-
lishments such as hospital cafeterias and
restaurants and are frequently attributable to
ineffective hand washing after defecation.
Shigellaare gram-negative, non-spore-
forming rods that are weakly motile and lac-
tose negative with low heat resistance.
Shigellaare generally not hearty and lack
resistance to environmental stresses. These
facultative anaerobes grow from 6 to 48ºC
with an optimum temperature of 37ºC. This
microorganism is primarily of human origin
and is spread to food by carriers and con-
taminated water. The pH range for Shigella
is 4.9 to 9.3. It requires a minimum Awof
0.94 with a maximum salt content of 4.0% to
5.0%.Shigellais a highly infectious microor-
ganism since the ingestion of less than 100 of
these bacteria can cause illness.Shigellaspp.
elaborate a toxin that has enterotoxic, neuro-
toxic, and psychotoxic activities responsible
for inflammatory intestinal responses.
Staphylococcal Foodborne Illness
S. aureus, a facultative, sphere-shaped,
gram-positive non-spore-forming microor-
ganism produces an enterotoxin that causes
an inflammation of the stomach and intes-
tines, known as gastroenteritis. Although
mortality seldom occurs from staphylococcal
food poisoning, the central nervous system
can be affected. If death occurs, it is usually
due to added stress among people with other
illnesses. The bacteria causing staphylococcal
food poisoning are widely distributed and
can be present among healthy individuals.
The pH range for S. aureusis 4.0 to 9.8 with
6.0 to 7.0 being optimum. It tolerates a water
activity as low as 0.86 in the presence of ca.
20% salt.
It appears that the handling of improperly
refrigerated food by infected individuals is one
of the greatest sources of contamination. The
most common foods that may cause staphylo-
coccal food poisoning are potato salad, cus-
tard-filled pastries, dairy products (including
cream), poultry, cooked ham, and tongue.
With ideal temperature and high contamina-
tion levels, staphylococci can multiply enough
to cause food poisoning without noticeable
changes in color, flavor, or odor.S. aureus
organisms are destroyed through heating at
66ºC for 12 minutes, but the toxin requires
heating for 30 minutes at 131ºC. Therefore, the
normal cooking time and temperature for
most foods will not destroy the enterotoxin.Trichinosis
This illness is transmitted to humans by
Trichinella spiralis, which can infect the flesh
of pork and wild game such as bear and
cougar. Most humans infected by this organ-
ism are asymptomatic. Symptomatic illness
includes gastroenteritis symptoms including
fever, nausea, vomiting, and diarrhea. Onset
time is approximately 72 hours with an infec-
tion time of up to 2 weeks. Initial symptoms
are followed by edema, muscle weakness, and
pain as the larvae migrate encysting the mus-
cles. Furthermore, respiratory and neurologi-
cal manifestations may occur. Death may
result if treatment is not administered. Pre-
vention is possible through protection from
contamination and cooking to 40ºC with con-
ventional cookery (i.e., gas and electric heat)
or 71ºC if microwave heating is practiced.
Other destruction methods include irradia-
tion or frozen storage of meat less than 15 cm
thick for 6 days at −29ºC or 20 days at −15ºC.Yersiniosis
Yersinia enterocolitica, a psychrotrophic
pathogen, is found in the intestinal tracts and