Analysis of enterotoxin production by Bacillus cereus from dairy products, food poisoning incidents and non-gastrointestinal infections

Abstract

Of 85 strains of Bacillus cereus isolated in Norway from dairy products, 59% were found to be enterotoxigenic, and 15% were psychotrophic. Six of the isolates (7%) were identified as potential psychotrophic food-poisoning strains as they were both enterotoxigenic and exhibited good growth at 6°C. Enterotoxin production was detected using the Western immunoblot technique, and a commercially available reversed passive latex agglutination (RPLA) assay (Unipath BCET-RPLA TD950). Both methods gave essentially the same results. In a separate study, the Western immunoblot and RPLA assays were used in a conjunction with the in vivo vascular permeability reaction (VPR) assay to determine enterotoxin production among 25 isolates of Bacillus cereus referred to the PHLS Food Hygiene Laboratory from incidents of diarrhoeal- and emetic-syndrome food poisoning and non-gastrointestinal infections. Eighty-four percent of these isolates were found to be enterotoxigenic by the Western immunoblot and the RPLA assays, and these results were in good agreement with those obtained by the VPR assay. In both studies, the BCET-RPLA kit proved to be a simple and reliable means for determining enterotoxin production by strains of Bacillus cereus.