CHARACTERIZATION OF BACILLUS-CEREUS IN RELATION TO TOXIN PRODUCTION

Several Bacillus cereus strains, isolated from different sources, were examined for their ability to produce diarrhoeal enterotoxin under se veral conditions using two immunological tests: reversed passive latex agglutination (Oxoid) and enzyme-linked immunosorbent assay (Tecra). There was no correlation between the results of the Oxoid and Tecra te st kits. Strains that had been implicated in foodborne outbreaks yield ed positive results with the Tecra test and negative results with the Oxoid test. All B. cereus strains tested yielded positive results with the Tecra test. Two strains implicated in foodborne outbreaks were st udied in more detail. Toxin production was observed in BHI, milk and r ice extract at any temperature allowing growth of the organisms. Enter otoxin was detectable only after concentrations of B. cereus reached g reater-than-or-equal-to 10(10) L-1. Static culture resulted in a facto r 10 lower enterotoxin production than culture with constant agitation . The D90-degrees-C, of spores of two strains involved in foodborne di sease outbreaks were 6 and 55 min., respectively. Spores of both strai ns germinated rapidly in BHI at 30-degrees-C. However germination in m ilk was significantly delayed.