1. Be Serious about B. cereus
Bacillus cereus

2. Bacillus cereus Gram positive Spore former Facultative aerobe
Germinates quickly (20-30 minutes)
pH range
Temperature range (41°F-122°F)
Optimum (95°F-104°F)

3. B. cereus Two types of food-borne intoxications (not infections)
Diarrheal form
Emetic (vomiting) form

4. Diarrheal form Onset time 6-18 hours Duration <24 hours
Resembles Clostridium perfringens food poisonings
Caused by heat-labile enterotoxin (heat-unstable)
Often affiliated with foods made with meat or vegetables

5. Emetic form Onset time 0.5-6 hours Duration <24 hours
Caused by heat-stable enterotoxin
Often affiliated with properly prepared fried rice that is not held at proper temperature
Resembles Staph aureus food poisonings

6. CDC Risk Factors 1. Food from unsafe sources 2. Inadequate cooking
3. Improper holding temperatures
4. Contaminated equipment
5. Poor personal hygiene

7. Outbreaks First reports in Europe in the early 1900’s
Linked to outbreaks in 1950’s
Worldwide recognition by the 1970’s
35 outbreaks reported in U.S. from

8. Maine Outbreak September 22, 1985
Restaurant patrons began exhibiting symptoms while at restaurant
11 persons of 36 served
Onset time 30 minutes to 5 hours.
Hibachi steak was positive for B. cereus
Fried rice, mixed veggies, & hibachi chicken were negative

9. Maine Outbreak (cont.) Fried rice made from leftover boiled rice
Storage practices unknown for boiled rice (may have been stored at room temperature)

10. Virginia Outbreak July 21, 1993 Two jointly owned child care centers
Catered lunch
Chicken fried rice was implicated
Rice was cooked the night before, cooled at room temperature then refrigerated
Rice was pan-fried with cooked chicken and delivered to centers by 10:30 am

11. Virginia Outbreak (cont.)
Rice was held w/o refrigeration
Served at noon w/o reheating
Median onset time 2 hours
CDC risk factor – improper holding temperatures

12. Sources of B. cereus Cereals Vegetables Spices
Pasteurized fresh & powdered milk
Dried beans
Potatoes

13. CDC Risk Factors Involved
Inadequate cooking
Improper holding temperatures
Contaminated equipment

14. References Bad Bug Book, USFDA MMWR 43(10):1994 Mar 18
MMWR 35(25):1986 Jun 27
Todar’s Online Textbook of Bacteriology –