Bacillus cereus is a Gram-positive, aerobic, rod-shaped bacterium capable of forming very resistant and highly adhesive endospores. Although it is normally a soil dweller, B. cereus is well adapted to growth in the intestinal tract of insects and mammals, where it acts as an opportunistic pathogen that may cause vomiting or diarrhea through the production of the small, heat-stable emetic toxin or the larger enterotoxin, respectively.