The natural environmental reservoir for B. cereus consists of decaying organic matter, fresh and marine waters, vegetablesand fomites, and the intestinal tract of invertebrates ,from which soil and food products may become contaminated, leadingto the transient colonization of the human intestine . Spores germinate when they come into contact with organic matter orwithin an insect or animal host.
B. cereus may be the most common aerobic spore bearer in manytypes of soil and in sediments, dust, and plants. B. cereus is also frequently present in food production environments dueto the adhesive nature of its endospores. This characteristicenables the bacterium to spread to all kinds of food. Because of the ubiquitous distribution of B. cereus in foodproducts, the bacterium is ingested in small numbers and becomespart of the transitory human intestinal flora. It is unclear, however, if the recovery of B. cereus in cultures of stool specimens is a function of germinating spores or thegrowth of vegetative cells.