MOLECULAR EPIDEMIOLOGY OF BACILLUS CEREUS FOOD POISONING

Abstract

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 fhe isoiates 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.