Abstract
Background: Bacillus cereus is a Gram-positive spore-forming 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 heat-labile enterotoxins:
HBL, NHE, and cytotoxin K. A heat-stable toxin, cereulide, is responsible for emesis.
Objectives: This study aimed to detect enterotoxigenic B. cereus isolates in cheese samples using the polymerase chain reaction
(PCR).
Materials and Methods: Two-hundred 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 hemolysin-encoding gene were used for the molecular detection of the toxins.
Results: 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 trimethoprim-sulfamethoxazole, respectively. The hblA and bal genes were amplified in all the B.
cereus isolates.
Conclusions: 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.