Be Serious about B. cereus

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Be Serious about B. cereus

• Bacillus cereus

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Bacillus cereus

• Gram positive
• Spore former
• Facultative aerobe
• Germinates quickly (20-30 minutes)
• pH range 4.5-9.3
• Temperature range (41F-122F)
• Optimum (95F-104F)

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B. cereus

• Two types of food-borne intoxications (not
  infections)
• Diarrheal form
• Emetic (vomiting) form

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Diarrheal form

• Onset time 6-18 hours
• Duration lt24 hours
• Resembles Clostridium perfringens food poisonings
• Caused by heat-labile enterotoxin (heat-unstable)
• Often affiliated with foods made with meat or
  vegetables

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Emetic form

• Onset time 0.5-6 hours
• Duration lt24 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

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CDC Risk Factors

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

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Outbreaks

• First reports in Europe in the early 1900s
• Linked to outbreaks in 1950s
• Worldwide recognition by the 1970s
• 35 outbreaks reported in U.S. from 1977-1984

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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

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Maine Outbreak (cont.)

• Fried rice made from leftover boiled rice
• Storage practices unknown for boiled rice (may
  have been stored at room temperature)

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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 1030 am

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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

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Sources of B. cereus

• Cereals
• Vegetables
• Spices
• Pasteurized fresh powdered milk
• Dried beans
• Potatoes

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CDC Risk Factors Involved

• Inadequate cooking
• Improper holding temperatures
• Contaminated equipment

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References

• Bad Bug Book, USFDA
• MMWR 43(10)1994 Mar 18
• MMWR 35(25)1986 Jun 27
• www.ag.iastate.edu/departments/foodsci/classes/fsh
  n420/bcereus.htm
• Todars Online Textbook of Bacteriology
  http//textbookofbacteriology.net/B.cereus.html