PCR-based detection of enterotoxigenic isolates of Bacillus cereus from tropical seafood.

ABSTRACT

Background & objectives: Bacillus cereus is an important enterotoxigenic food borne pathogen. The present study was undertaken to assess the occurrence of B. cereus in tropical fish and evaluation of virulent gene specific PCR for differentiation of diarrhoeal enterotoxin producing isolates of B. cereus from non enterotoxigenic isolates. Methods: Selective plating on polymixin-pyruvate-egg yolk-mannitol-bromocresol purple agar (PEMPA) was used for isolation of B. cereus from finfish, prawn and clams. Enterotoxin producing ability of all 42 isolates obtained from the samples was judged by reverse passive latex agglutination (RPLA) test and the presence of different virulent genes i.e. hbla, bceT and entFM was screened by PCR. Results: B. cereus and enterotoxigenic B. cereus were found to be in 36.7 and 29.41 per cent of fish samples, respectively. All the diarrhoeal enterotoxin producing isolates showed the presence of hbla gene, but hbla gene was not present in any of the non-enterotoxigenic isolates tested in this study. Interpretation & conclusions: Our findings indicated that hbla gene specific PCR can be employed for differentiation of enterotoxigenic B. cereus isolates from non-enterotoxigenic isolates.