Bacillus cereus

Compiled By: Julie A. Albrecht, Ph.D., Associate Professor

The Organism: Bacillus cereus is a facultative anaerobic spore forming bacteria. It is widespread in nature and in foods, especially in the spore state.

PDF Fact Sheet

Sources of the organism:

Unpasteurized milk
Cereals and starch
Herbs and spices

Associated foods:

Meat pies
Cooked rice and fried rice
Starchy foods (potato, pasta)
Food mixtures (soups, casseroles, sauces)

Microorganism Characteristics: Gram positive facultative anaerobic spore forming rod.

Growth conditions:

Temperature range: 10-49°C (50-91°F)
Optimum Temperature: 30°C (86°F)
pH range: 4.9-9.3
Lowest reported Aw for growth: 0.93

The Disease: The Disease: Bacillus cereus can cause two distinct types of illnesses: 1) a diarrheal illness with an incubation time of approximately 10 to 16 hours, and 2) an emetic (vomiting) illness with an incubation time of one to six hours.

Symptoms include:

Abdominal cramps
Watery diarrhea

Onset time:

Type 1: 10-16 hours
Type 2: 1-6 hours

Infective Dose:

Large numbers (more than 105 CFU/gm) of viable Bacillus cereus cells need to be consumed for symptoms of the illness to develop.

Duration of symptoms:

Usually 1 day


  • Thoroughly cook ground meat products.
  • Cool cooked products to 41°F within 4 hours
  • Hold hot foods at or above 140°F.