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Bacillus cereus -- Maine

On September 22, 1985, the Maine Bureau of Health was notified of a gastrointestinal illness among patrons of a Japanese restaurant. Because the customers were exhibiting symptoms of illness while still on the restaurant premises, and because uncertainty existed as to the etiology of the problem, the local health department, in concurrence with the restaurant owner, closed the restaurant at 7:30 p.m. that same day.

Eleven (31%) of the approximately 36 patrons reportedly served on the evening of September 22 were contacted in an effort to determine the etiology of the outbreak. Those 11 comprised the last three dining parties served on September 22. Despite extensive publicity, no additional cases were reported.

A case was defined as anyone who had vomiting or diarrhea within 6 hours of dining at the restaurant. All 11 individuals were interviewed for symptoms, time of onset of illness, illness duration, and foods ingested. All 11 reported nausea and vomiting; nine reported diarrhea; one reported headache; and one reported abdominal cramps. Onset of illness ranged from 30 minutes to 5 hours (mean 1 hour, 23 minutes) after eating at the restaurant. Duration of illness ranged from 5 hours to several days, except for two individuals still symptomatic with diarrhea 2 weeks after dining at the restaurant. Ten persons sought medical treatment at local emergency rooms on September 22; two ultimately required hospitalization for rehydration.

Analysis of the association of food consumption with illness was not instructive, since all persons consumed the same food items: chicken soup; fried shrimp; stir-fried rice; fried zucchini, onions, and bean sprouts; cucumber, cabbage, and lettuce salad; ginger salad dressing; hibachi chicken and steak; and tea. Five persons ordered hibachi scallops, and one person ordered hibachi swordfish. However, most individuals sampled each other's entrees.

One vomitus specimen and two stool specimens from three separate individuals yielded an overgrowth of Bacillus cereus organisms. The hibachi steak was also culture-positive for B. cereus, although an accurate bacterial count could not be made because an inadequate amount of the steak remained for laboratory analysis. No growth of B. cereus was reported from the fried rice, mixed fried vegetables, or hibachi chicken.

According to the owner, all meat was delivered 2-3 times a week from a local meat supplier and refrigerated until ordered by restaurant patrons. Appropriate-sized portions for a dining group were taken from the kitchen to the dining area and diced or sliced, then sauteed at the table directly in front of restaurant patrons. The meat was seasoned with soy sauce, salt, and white pepper, open containers of which had been used for at least 2 months by the restaurant. The hibachi steak was served immediately after cooking.

The fried rice served with the meal was reportedly customarily made from leftover boiled rice. It could not be established whether the boiled rice had been stored refrigerated or at room temperature. Reported by J Vandeloski, Portland City Health Dept, KF Gensheimer, MD, State Epidemiologist, Maine Dept of Human Svcs; Enteric Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: B. cereus is an aerobic, spore-forming, gram-positive rod with a ubiquitous distribution in the environment. Spores of B. cereus have been found in a wide variety of cereals, pulses, vegetables, spices, and pasteurized fresh and powdered milk. Food-poisoning can result from toxins elaborated by germinating organisms, which most commonly follows from inadequate refrigeration and subsequent reheating of foods that have already been cooked.

Two different clinical syndromes appear to be associated with B. cereus food poisoning, which correspond to two different toxins elaborated by the bacteria. A diarrheal syndrome similar to Clostridium perfringens food poisoning with an average incubation period of 10-12 hours has been associated with a heat-labile toxin elaborated by B. cereus. An emetic syndrome similar to staphylococcal food poisoning, with an average incubation period of 1-6 hours, has been associated with a heat-stable toxin from B. cereus (1).

The emetic syndrome has almost always been associated with fried rice served in Oriental restaurants. The common practice of storing boiled rice at room temperature for subsequent preparation of fried rice has generally been implicated in such outbreaks. However, a recent, well-documented outbreak of the emetic syndrome of B. cereus in a British prison implicated beef stew (2). This was thought to be caused by adding to the stew vegetables that were cooked a day earlier.

Fresh meat cooked rapidly, then eaten immediately, seems an unlikely vehicle for B. cereus food poisoning. The laboratory finding of B. cereus in a foodstuff without quantitative cultures and without accompanying epidemiologic data is insufficient to establish its role in the outbreak. A negative culture of fried rice eaten with the meal does not exclude the obvious vehicle; reheating during preparation may eliminate the bacteria in the food without decreasing the activity of the heat-stable toxin. While the question of the specific vehicle remains incompletely resolved, the clinical and laboratory findings substantially support B. cereus as the cause of the outbreak.

Most episodes of food poisoning undoubtedly go unreported, and in most of those reported, the specific pathogens are never identified. Alert recognition of the clinical syndrome and appropriate laboratory work permitted identification of the role of B. cereus in this outbreak.

References

  1. Terranova W, Blake PA. Bacillus cereus food poisoning. N Engl J Med 1978;298:143-4.

  2. CDC. Communicable disease report, no. 21, May 25, 1984:3.



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