Detection of Hemolysin BL Gene of Bacillus cereus IsolatesC. Wiwat* and R. Thiramanas
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Hemolysin BL (HBL) is the multi-component enterotoxin causing diarrheal type of Bacillus cereus food poisoning. The hbl operon of B. cereus was divided into 4 coding sequences (CDS) and identified as hblC, hblD, hblA and hblB genes consisting of 1,319, 1,221, 1,128 and 1,401 nucleotides encoding proteins of 439, 406, 375 and 466 amino acids with predicted sizes of 49.3, 43.8, 41.7 and 52.3 kDa, respectively. One hundred of B. cereus isolates were detected for the presence of each hbl gene by multiplex PCR and HBL production by discontinuous hemolysis on HBL sheep blood agar and Bacillus cereus Enterotoxin-Reverse Passive Latex Agglutination (BCET-RPLA) test kit. The results showed that 47 of 100 B. cereus isolates (47%) were detected by multiplex PCR with all hbl genes and gave positive result with RPLA test. Forty-one of 47 isolates (87.2%) produced discontinuous hemolysis on HBL sheep blood agar. However, this pattern was not observed clearly in 6 of 47 isolates (12.8%). In addition, B. cereus isolate E82/44 gave multiplex PCR positive with only 3 hbl genes, hblA, hblC and hblD, also showed positive result with RPLA test and produced discontinuous hemolysis.
Keyword:
Bacillus cereus, Hemolysin BL, Enterotoxin, Food poisoning.
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