Bacillus cereus is a Gram positive rod-shaped bacterium responsible for outbreaks of food poisoning, and more rarely wound infections, septicaemia and meningitis. The bacteria multiply rapidly (once every 20-30 mins) under ideal conditions (35 - 40°C) and also produce spores which are very resistant to heat. The bacteria are found everywhere - in the soil, dust and air, as well as being carried by humans and animals or in foods. Good kitchen practice is essential to prevent rapid reproduction and avoid food poisoning. Food should be kept at above 50°C or below 4°C; cooling should take place as rapidly as possible, especially when dealing with cooked rice.
The bacteria produce a number of chemicals including proteases, phospholipases, hemolysins and enterotoxins. Two distinct types of food poisoning may occur, depending on the type of toxin produced by the bacteria.
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The emetic type, is characterised by very rapid onset of nausea and vomiting - occuring between half an hour and 6 hours of consumption. This is usually associated with eating rice products, although other starchy foods can also carry this type of contamination.
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The second type causes watery diarrhea and stomach cramps and symptoms begin between 6 and 15 hours of eating the contaminated foods, typically milk, meat and fish products.
In both cases symptoms persist for about 24 hours requiring no further treatment.