What is
Bacillus cereus?

Bacillus cereus might cause many more cases of foodborne illness than is known. One reason it’s under-reported may be that most people have fairly mild, brief symptoms, so they don’t seek medical attention. Like other types of foodborne pathogens, it can cause serious illness in some people.

Often called “B. cereus” this bacterium causes two different types of sickness.

B. cereus causes two different types of illness

Both types can cause serious complications, though this is rare in otherwise healthy people.
Generally speaking, they’ll both go away by themselves.

People who are immunocompromised (because of other diseases or medications that weaken their immune system) are much more likely to suffer serious consequences.

The first type of B. cereus
causes diarrhea and cramps

  • After contaminated food is eaten the bacteria make a toxic substance in the small intestine.
  • This can lead to diarrhea, cramps, and, sometimes, nausea (but usually not vomiting). 
  • Symptoms start in about 6 to 15 hours and usually clear up within a day or so.
  • A wide variety of foods, including meats, milk, vegetables, and fish, have been associated with the diarrheal-type food poisoning.

The second type of B. cereus
causes nausea and vomiting

  • The second type occurs when B. cereus makes a different kind of toxin in contaminated food, causing nausea and vomiting.
  • Generally, outbreaks of the vomiting-type have been associated with rice products; however, other starchy foods, such as potato, pasta, and cheese products, also have been implicated. 
  • Symptoms start 0.5 to 6 hours after consumption of contaminated food.
Symptoms of B. cereus diarrheal-type food poisoning mimic those of Clostridium perfringens.
Symptoms of B. cereus vomiting-type food poisoning parallel those caused by
Staphylococcus aureus foodborne intoxication.

Who can get B. cereus?

All people are believed to be susceptible to B. cereus food poisoning.

Preventing Bacillus cereus infection

One of the most important things you can do to protect yourself from infection with B. cereus is to keep your food refrigerated at 40ºF or lower.

The reason is that, at higher temperatures, B. cereus can form spores – a survival mode in which they make an inactive form that can exist without nutrition and that develops very tough protection against the outside world – that grow and turn into more B. cereus bacteria.

The more bacteria, the more toxin, and the greater the chance that you’ll get sick.

Cooking may kill the bacteria, but it might not disable the toxin that causes the vomiting-type of illness. And don’t stop at refrigeration, because a related Bacillus bacterium can survive and grow at refrigerator temperature.

Add other food‐safety measures/good hygiene, like washing your hands, and washing foods (not meat or poultry), utensils, cutting boards and preparation space. Keep raw and cooked foods separate.

Food and Drug Administration (FDA). Bad Bug Book, Foodborne Pathogenic Microorganisms and Natural Toxins.
Second Edition. Bacillus cereus, pp.92. 2012.

Food Safety is a complex issue find out more from the FDA