Bacillus cereus is a soil dwelling bacteria responsible for 2 – 5% of cases of food poisoning worldwide. All people are susceptible to Bacillus cereus food poisoning, which can occur year-round in any part of the world. Bacillus cereus has been recognized as a food poisoning agent since 1955.

There are two types of Bacillus cereus food poisoning. One is a long-incubation form with diarrhea as the main symptom, and the other is a short-incubation form that causes bouts of nausea and vomiting. In both cases, the illness occurs due to the presence of the bacteria in improperly cooked foods, which can be further compounded if the food is improperly refrigerated, which causes the spores of the bacteria to germinate. The Bacillus cereus bacteria can multiply rapidly and produces a heat resistant toxin that cannot be eliminated by cooking or reheating. The bacteria or its toxin cannot be detected by smell or sight.

A variety of foods have been associated with the long-incubation form of Bacillus cereus food poisoning. These include meat, vegetables, milk, and fish. Mixtures such as sauces, soups, casseroles, and pastries have also been linked to outbreaks of food poisoning. The short-incubation version of the illness is mainly associated with cooked rice that has been improperly refrigerated, such as the fried rice found in some Chinese restaurants. Rice that has been cooked and then held at warm temperatures for an extended period of time seems to be a preferred host for this type of bacteria, and it grows quickly in these conditions. Other foods rich in starch, such as pasta and potato products, have also been known to transmit the illness.

Sickness can be caused by consuming less than 150 cells of the Bacillus cereus bacteria. The short-incubation food poisoning results in nausea and vomiting 1 to 5 hours after consuming the contaminated food. The long-incubation version creates heavy nausea, abdominal pain, and diarrhea 8 to 16 hours after ingesting the bacteria. A small volume of diarrhea may be present with the short-incubation version as well. Complications from Bacillus cereus food poisoning are rare.

Most cases of Bacillus cereus food poisoning resolve themselves without medical treatment. Rehydration, either orally or intravenously, may be needed to replace fluids lost through vomiting or diarrhea. Antibiotics are normally not given, as the bacteria have been found to be resistant to penicillin. This illness cannot be spread by person to person contact. The only way to contract the illness is by consuming contaminated food.

The number of cases of Bacillus cereus food poisoning reported annually ranges from 6 to 50 cases. The occurrence of the illness may be much greater as many cases are not reported and do not require medical treatment. Many people who contract this illness just wait for the symptoms to pass and self-treat themselves at home with rest and fluids. Many reported cases are due to an outbreak of Bacillus cereus food poisoning affecting a number of people, usually because they all ate the same food at the same restaurant.