Saturday, January 15, 2011

Bacillus cereus

Bacillus cereus is a gram positive, spore forming, motile, aerobic rod that also grows well anaerobically.

Bacillus cereus like Clostridium perfringes is present in the environment and requires large numbers of bacterial cells to cause infection.

Bacillus cereus has been known to be cause of food poisoning since the early 1950s.

It has two major strains: one causes diarrhea within six to fifteen hours of consumption of tainted food; the other ‘emetic syndrome’ causes nausea and vomiting within a half hour to six hours after ingestion.

The diarrheal type is often misdiagnosed as C. perfringes and the type that causes nausea and vomiting is often mistaken as Staphylococcus aureus infection.

The diarrheal type of food poisoning is caused by complex enterotoxin during vegetative growth of Bacillus cereus in the small intestine.

While the other one emetic toxin is preformed during the growth of cells in the foods. Diarrhea is not a predominant feature in this type of illness.

A wide variety of foods can harbor the bacteria.

The diarrheal type favors meats, milk, vegetables and fish, while the vomiting type illness is most often associated with rice products such as fried rice, but it can also occur in starchy foods like potatoes, pasta and casseroles.

The diarrheagenic toxin is inactivated by heating for 5 min at 50 degree C, although its thermostabiltiy is reported to be greater.

Both types of illness are generally not serious, except in young children, older adults and others who are immune compromised and may not have the stamina to combat the associated dehydration.

Recovery for Bacillus cereus food poisoning is normally within 24 hours, with no complications.
Bacillus cereus
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