Caister Academic Press

Bacillus cereus

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A review of Bacillus cereus.

Bacillus cereus

Adapted from Per Einar Granum in Foodborne Pathogens: Microbiology and Molecular Biology
Bacillus cereus: The Bacillus cereus group comprises six members: Bacillus anthracis, Bacillus cereus, Bacillus mycoides, Bacillus pseudomycoides, Bacillus thuringiensis and Bacillus weihenstephanensis. These species are closely related and should be placed within one species, except for Bacillus anthracis that possesses specific large virulence plasmids. Bacillus cereus is a normal soil inhabitant and is frequently isolated from a variety of foods, including vegetables, dairy products and meat. It causes an emetic or a diarrhoeal type of food-associated illness that is becoming increasingly important in the industrialized world. Some patients may experience both types of illness simultaneously. The diarrhoeal type of illness is most prevalent in the western hemisphere, whereas the emetic type is most prevalent in Japan. Desserts, meat dishes, and dairy products are the foods most frequently associated with diarrhoeal illness, whereas rice and pasta are the most common vehicles of emetic illness. The emetic toxin (cereulide) has been isolated and characterized; it is a small ring peptide synthesised non-ribosomally by a peptide synthetase. Three types of Bacillus cereus enterotoxins involved in foodborne outbreaks have been identified. Two of these enterotoxins are three-component proteins and are related, while the last is a one-component protein (CytK). Deaths have been recorded both by strains that produce the emetic toxin and by a strain producing only CytK. Some strains of the Bacillus cereus group are able to grow at refrigeration temperatures. These variants raise concern about the safety of cooked, refrigerated foods with an extended shelf life. Bacillus cereus spores adhere to many surfaces and survive normal washing and disinfection (except for hypochlorite and UVC) procedures. Bacillus cereus foodborne illness is likely underreported because of its relatively mild symptoms, which are of short duration. However, consumer interest in precooked chilled food products with a long shelf life may lead to products well suited for Bacillus cereus survival and growth. The availability of such foods could increase the prominence of Bacillus cereus as a foodborne pathogen.

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