Identification of Staphylococcus aureus Causing Contamination in Raw Beef and Meat-Processing Environments in Ulaanbaatar, Mongolia.

Abstract

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium capable of causing a range of infections and displaying significant antibiotic resistance. S. aureus can exhibit resistance to multi-antibiotics, particularly penicillin, methicillin, linezolid, and daptomycin. The prevalence of methicillin-resistant S. aureus (MRSA) ranges from 10%-50% in China and Russia, neighboring countries of Mongolia. This study aimed to assess S. aureus contamination in raw beef samples and surface swabs from meat-processing areas and markets, while detecting, as well as to detect virulence and resistance genes in the isolates. A total of 156 raw beef samples and 131 surface swabs were collected and analyzed using ISO 6888-1:2021 standards. The nucA gene specific to S. aureus was amplified by PCR, and antibiotic susceptibility was evaluated using the Kirby-Bauer disk diffusion method. Resistance genes (mecA, mecC, vanA, and vanB) and virulence genes (sea, sed, tsst, eta, and etb) were detected via PCR. The results showed contamination rates of 26.9% in raw beef and 15.3% in surface swabs. The isolates exhibited high resistance to oxacillin, ampicillin, and penicillin in meat samples and to oxacillin, tetracycline, azithromycin, and clindamycin in surface swabs. No resistance genes for vancomycin or methicillin (mecC, vanA, vanB) were detected. Virulence genes, including tsst (14.5%), sea and etb (9.7%), eta (3.2%), and sed (1.6%), were identified. Contamination was more prevalent in centers responsible for both transportation and sales, compared to meat-processing areas. These findings highlight the need for stricter hygiene and handling practices in meat transport and markets to reduce S. aureus contamination and limit the spread of resistant strains.