Molecular epidemiology of Bacillus cereus food poisoning.

OBJECTIVES To investigate the potential use of DNA techniques in epidemiological diagnosis of Bacillus cereus food poisoning. SUBJECTS Fifty six B. cereus isolates from milk were studied. DESIGN The 56 B. cereus isolates were characterised into enterotoxin positive (27 isolates) and enterotoxin negative (29 isolates) using reverse passive latex agglutination technique. SETTING Plasmid and genomic DNA were isolated from all the B. cereus isolates. The plasmid DNA was analysed by gel electrophoresis, while genomic DNA was used for restriction endonuclease and toxin gene analyses. MAIN OUTCOME MEASURES Plasmid profile analysis, restriction endonuclease analysis of genomic DNA, and test for bceT and hblA genes by polymerase chain reaction and gene probing. RESULTS Seventy two per cent of the isolates contained one to five plasmids of molecular sizes between 0.1 to 60 mDa. Restriction analysis of genomic DNA gave different restriction patterns among enterotoxin positive and enterotoxin negative isolates. A polymerase chain reaction assay detected bceT gene in 41.1% of the isolates, 16% of which tested positive for enterotoxin with B. cereus enterotoxin reverse passive latex agglutination (BCET-RPLA) kit, while hblA gene was detected in all the enterotoxin positive isolates. BceT and hblA gene probes detected the respective genes in all the isolates that also tested positive for toxin genes by polymerase chain reaction. CONCLUSION DNA techniques provide an alternative approach to the diagnosis of enterotoxigenic B. cereus.