Background:
Food safety is a serious challenge in the face of increasing population and diminishing resources. Staphylococcus aureus is a critical foodborne pathogen characterized by its capability to secret a diverse range of heat-resistant enterotoxins. Antibiotic usage in dairy herds resulted in the occurrence of antimicrobial resistance patterns among bacterial species, which were consequently transmitted to human via the dairy products. Lactic acid bacteria produce bacteriocins, which provide an excellent source of natural antimicrobials with the further advantage of being environmentally friendly and safe.
Aim:
Detection of MDR S. aureus isolates in concerned samples, molecular characteristics, biofilm production and the inhibitory role of LAB against it.
Methods:
Random samples of raw milk and other dairy products were analyzed for S. aureus isolation. Phenotypic and genotypic assessment of antimicrobial resistance was performed, in addition to detection of classical enterotoxin genes of S. aureus. Finally, evaluation of antimicrobial action of some lactobacillus strains against S. aureus.
Results:
Incidence rates of presumptive S. aureus in raw milk, kariesh cheese and yoghurt samples were 50%, 40% and 60%, respectively. Highest resistance of S. aureus was to Kanamycin (100%) and Nalidixic acid (89.3%), respectively. (78.66%) of S. aureus were MDR. (11.1%) of S. aureus carried mecA gene. In concern with enterotoxins genes, PCR showed that examined isolates harbored sea with a percentage of (22.2%), while sed was found in (11.1%) of isolates. Regarding biofilm production, (88.88%) of S. aureus were biofilm producers. Finally, agar well diffusion showed that L. acidophillus had the strongest antimicrobial action against S. aureus with inhibition zone diameter ranged from 18-22mm.
Conclusion
There is a widespread prevalence of MDR S. aureus in raw milk and dairy products. Production of staphylococcal enterotoxins, as well as biofilm production are responsible for public health risks. Therefore, installing proper hygienic routines and harsh food safety policies at food chain levels is substantial.
Key words: MecA gene, Staphylococcal enterotoxins, Biofilm formation, Lactic acid bacteria
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