Bacillus cereus is a Gram-positive, rod-shaped, facultative anaerobic bacterium that can produce toxins which cause food poisoning. It belongs to the Bacillus genus.
After ingestion, B. cereus experiences in the human gastro-intestinal tract abiotic physical variables encountered in food, such as acidic pH in the stomach and changing oxygen conditions in the human intestine.
Foods incriminated in past outbreaks include cooked meat and vegetables, boiled or fried rice, vanilla sauce, custards, soups, and raw vegetable sprouts. B. cereus causes two types of illness; emetic (nausea and vomiting) and diarrheal. Different toxins and pathogenic factors are responsible for diarrheal syndrome, like nonhemolytic enterotoxin Nhe, hemolytic enterotoxin Hbl, enterotoxin FM and cytotoxin K, while emetic syndrome is caused by the depsipeptide cereulide toxin.
The Bacillus cereus group comprises seven closely related species: B. cereus sensu stricto (referred to herein as B. cereus), B. anthracis, B. thuringiensis, B. mycoides, B. pseudomycoides, and B. cytotoxicus.
The traditional method of B. cereus detection is based on the bacterial culturing onto selective agars and cells enumeration. On MYP (Mannitol Egg Yolk) medium, colonies of B. cereus have a pink–purple color, surrounded by a characteristic halo formed of pink precipitation, which permits their identification.
Facultative anaerobes of Bacillus cereus
