Key to virulence in food poisoning
In total, 100 strains of the bacterium from different foods in varying environments from various European regions were studied and a database has been established. Included are mesophilic and psychrophilic variants and emetic and diarrhoeic strains. These strains have been characterized for virulence features, ecology and their behaviour in the food production chain. The gene responsible for production of the emetic toxin has been identified and this is used to detect strains that produce the toxin. Efficient screening methods for the genes responsible for toxicity and for detection of toxin producing strains are now available. One of the three components of an enterotoxin produced by the bacterium is necessary for toxicity. The dose of emetic toxin required for emesis has been ascertained. Contamination routes have been identified. Bedding material in dairy farms, soil and raw vegetables are all sources of B cereus. Heat resistance of spores varies greatly. All emetic strains studied produce spores with the highest heat resistance. Spores from psychrophilic strains in vegetables show low heat resistance as opposed to those from mesophiles in texturing agents that show high heat resistance. Important variables in emetic toxin production in infant food are food composition and aeration. Information on factors that affect the severity of food poisoning caused by B cereus can be used to improve dose response during treatment and to assess the risk of their presence and development in food.
