Abstract: To study the epidemiological characteristics of Staphylococcus aureus isolates from yak slaughterhouses, 150 biological samples were collected from a yak slaughterhouse in Chengdu. Strains suspected of being S. aureus were isolated using Baird-Parker medium and the ones carrying the heat-resistant nuclease gene (nuc) unique to S. aureus were identified by polymerase chain reaction (PCR). The S. aureus strains were examined for whether they carried 21 enterotoxin genes, 6 virulence genes, 4 disinfectant resistance genes, or 14 drug resistance genes. The susceptibility of the S. aureus isolates to 24 antibiotics was detected by disk diffusion method. The results showed that 67 S. aureus strains were isolated and identified from the 150 samples with a detection rate of 44.67%. The detection rate was relatively high in carcass and environmental swab samples, 56.67% and 51.61%, respectively. A total of 12 enterotoxin genes were detected in the isolates, among which the carrying rates of selx, seu and sej genes were high. We also confirmed the presence of the virulence genes (hlα, hlβ, eta, etb, pvl, and tsst-1), the disinfectant resistance genes (qacA/B, qacG, and qacH), and 11 drug-resistant genes. Eleven positive bands were found for antibiotic resistance genes. Notably, the detection rate of the methicillin-resistant gene (mecA) was 62.69%, and the detection rates of the aminoglycoside-resistant gene (aac6’/aph2’) and the macrolide-resistant gene (erm) were high. Most of the 67 isolates had multi-drug resistance. The epidemiological characteristics of S. aureus during the slaughter process of yaks demonstrated contamination with multi-drug resistant S. aureus with carrying virulence genes, which may pose potential threats to consumers’ health through the food chain. This study provides reference for evaluating the risk of S. aureus contamination during yak slaughter.

Key words: yak slaughter; Staphylococcus aureus; isolation and identification; virulence gene; drug-resistant phenotype