Molecular characterization and genotyping of Bacillus cereus isolated from buffalo raw milk and milk products

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Bacillus cereus, a ubiquitous organism, is mainly responsible for foodborne illness. The present study was conducted in order to determine the incidence, virulence gene and antibiogram profiles along with genetic diversity of B. cereus isolated and confirmed through PCR assay from different milk and milk products (raw milk, basundi, burfi, junnu (colostrum milk pudding), kalakhand and khoa). B. cereus was isolated from 73 (22.81%. 73/320) different samples by cultural method (20 raw milk, 9 basundi, 11 burfi, 3 flavoured milk, 10 junnu, 10 kalakand and 10 khoa samples). Of the 73 cultural positive isolates, 31 (9.68%, 31/320) were confirmed to be B. cereus by species specific PCR (9.68%) with 8% (12/150), 15% (3/20), 12.1% (4/33), 11.8% (2/17), 10.8% (4/37) and 21.4% (6/28) occurrence in raw milk, basundi, burfi, colostrum milk pudding (junnu), kalakhand and khoa samples, respectively and none of the flavoured milk and ice cream samples were positive for B. cereus by PCR The virulence genes, nheA, nheB, entFM and nheC were found. None of the isolates were positive for the hbl complex and cytK genes. The three component Nhe complex (all nheA, nhe B and nheC genes) was detected in some isolates, indicating the possibility of non-haemolytic diarrheal food poisoning syndrome. All the isolates were resistant to beta-lactam antibiotics but highly sensitive to gentamicin and tetracycline. ERIC-PCR (Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction) found to be superior to REP- PCR (Repetitive Extragenic Palindromic PCR) in differentiating the B. cereus isolates in this study.