Fundamental Food Microbiology, Third Edition - Fuad Fathir

FOODBORNE TOXICOINFECTIONS 397
F. Food Association
Many types of food can contain small numbers of cells and spores of Bac. cereus. 6–8
Consumption of these foods does not cause the disease. However, when these foods
are abused to facilitate spore germination and cell multiplication, the population of
live cells can reach the high levels necessary for the disease. In the diarrheal
outbreaks, a variety of foods, including vegetables, salads, meats, pudding, casseroles,
sauces, and soups, has been implicated, mostly because of their improper
cooling. However, in the emetic form, outbreaks mostly involve rice and sometimes
other starchy foods. Table 26.2 presents a list of foods associated with Bac. cereus
gastroenteritis outbreaks in the U.S. from 1973 to 1987. Although many foods are
listed, the most predominant was fried rice in Chinese restaurants (Chinese rice
syndrome). Investigations revealed that, following boiling for preparation, the rice
is kept at room temperature for a long time. The surviving (or contaminated) spores
germinate, and the cells multiply to high levels before the rice is served. 1,6–8
G. Prevention
The predominating contributing factors associated with Bac. cereus gastroenteritis,
in order of relative importance, are improper holding temperature, contaminated
equipment, inadequate cooking, and poor personal hygiene. The heat treatment
normally used in food preparation, except for pressure cooking, may not destroy
Bac. cereus spores. The most important control measure is to keep food at a temperature
at which the spores do not germinate and cells do not grow. This can be
achieved by uniform quick chilling of the food to ca. 4 to 5�C or holding the food
above 60�C. Quick chilling can best be accomplished by storing a food in a shallow
container, no more than 2 to 3 in. (5 to 6 cm) thick. Because Bac. cereus cells, given
sufficient time, can grow and produce toxins at refrigerated temperature (�4�C), a
food should not be stored at low temperatures for long periods of time. This means
that preparation of a food well in advance should be avoided. Because cells can get
in a food through cross-contamination, proper sanitary measures should be adopted
while handling a food. Finally, as live cells are necessary for the symptoms, there
should be uniform reheating a suspected food to above 75�C before serving. However,
heating may not destroy heat-stable toxins associated with emetic symptoms. 3,6
\
Table 26.2 Food Types Associated with Bac. cereus Gastroenteritis from 1973 to
1987 in the U.S.
No. of
No. of
Food Type Outbreaks % Food Type Outbreaks %
Chinese food 24 41.5 Finfish 1 1.7
Mexican food 5 8.6 Shellfish 2 3.4
Beef 3 5.2 Ice cream 1 1.7
Chicken 1 1.7 Other 8 13.8
Turkey 1 1.7 Unknown 9 15.5
Vegetables 3 5.2