Bacillus cereus is a spore-forming bacterium that can be frequently isolated from soil and some food and which produces toxins. These toxins can cause two types of illness: one type characterized by diarrhea (long incubation, 8-16 hours) and the other by nausea and vomiting (short incubation, 1-6 hours). The short-incubation form is most often associated with rice dishes that have been cooked and then held at warm temperatures for several hours. Long-incubation B. cereus food poisoning is frequently associated with meat or vegetable containing foods, after cooking. 

The bacterium has been isolated from dried beans and cereals, and from dried foods such as spices, seasoning mixes and potatoes. The short-incubation or emetic form of the disease is diagnosed by the isolation of B. cereus from the incriminated food. The long-incubation or diarrheal form is diagnosed by isolation of the organism from stool and food.