detection of hbla and bal genes in bacillus cereus isolates from cheese samples using the polymerase chain reaction

Bacillus cereus is a grampositive sporeforming bacterium, which causes food poisoning. spores enable the persistence of b. cereus in the environment, and b. cereus strains can tolerate adverse environmental conditions, such as temperature and insufficient nutrients. b. cereus causes food poisoning via the production of two enterotoxins. most isolates produce toxins leading to diarrhea (enterotoxins) and vomiting (emetic forms). diarrhea is caused by the production of three different heatlabile enterotoxins: hbl, nhe, and cytotoxin k. a heatstable toxin, cereulide, is responsible for emesis. this study aimed to detect enterotoxigenic b. cereus isolates in cheese samples using the polymerase chain reaction (pcr). twohundred pasteurized (n = 100) and nonpasteurized (n = 100) cheese samples were collected. the initial isolation was performed on pemba specific medium. antibiotic susceptibility testing was performed using several antibiotic disks, according to the guidelines of the clinical laboratory and standards institute. specific primers amplifying the hbla enterotoxinencoding gene and bal hemolysinencoding gene were used for the molecular detection of the toxins. ten samples were positive for the presence of b. cereus, with both gram staining and biochemical reactions. all the isolates were resistant to penicillin and ampicillin but susceptible to vancomycin, erythromycin, and ciprofloxacin. six and three isolates were resistant to tetracycline and trimethoprimsulfamethoxazole, respectively. the hbla and bal genes were amplified in all the b. cereus isolates. the prevalence of b. cereus among the cheese samples was low. all the isolates were positive for genes encoding the hbla enterotoxin and bal toxin.