Abstract
Background
Bacillus cereus is known as one of the major foodborne pathogens that often associated with the contamination of raw milk and dairy products. The aim of this study was to isolate the emetic toxin-producing Bacillus cereus (B. cereus) in unpasteurized traditional dairy products. Also, the antimicrobial resistance pattern was investigated in the isolates.
Methods
For this purpose, 150 samples of unpasteurized ice cream, cheese, doogh, curd and butter (prepared by traditional method) were randomly selected from the market from March 2019 to July 2020. Samples were evaluated for the presence of emetic toxin-producing B. cereus using culture and PCR method.
Results
Sixteen of 150 (10.66%) samples were contaminated with B. cereus. This pathogen was isolated from one (3.33%) sample of ice cream, 9 (30%) of doogh, 6 (20%) of curd in the mean contamination levels of 2.0 ± 0.0 and 4.4 ± 0.6, respectively. B. cereus was not isolated from cheese and butter samples. The contamination level of curd to this bacterium was significantly higher than other products (p < 0.05). PCR results showed that 14 (78.5%) of 16 isolates contained the ces gene. The results of the antibiogram test showed that B. cereus isolates were resistant to penicillin, cefazolin and co-trimoxazole (trimethoprim-sulfamethoxazole), semi-sensitive to vancomycin and erythromycin, and sensitive to gentamicin, ciprofloxacin and clindamycin. Also, 31.25% of isolates were resistant to six antibiotics simultaneously.
Conclusion
The findings of present study showed that traditional unpasteurized dairy products could provide a great potential for intoxication by antimicrobial-resistance and emetic toxin-producing strains of B. cereus.
Detection of emetic toxin (ces) gene and antimicrobial susceptibility of Bacillus cereus isolates from Iranian traditional dairy products