Abstract
Staphylococcus aureus is an important cause of food intoxication, which has the potential to induce diverse infections, toxinoses and life-threatening diseases among humans and animals. This study investigated the prevalence, antimicrobial resistance, and genetic diversity of S. aureus and methicillin-resistant S. aureus (MRSA) in retail raw meat from Shandong (March 2021-October 2022). The distribution of virulence genes, antimicrobial susceptibility, and genetic diversity of these isolates were analyzed. From a total of 442 samples, 87 (19.7%) S. aureus and 11 (2.5%) MRSA were isolated. According to the antimicrobial susceptibility testing, it was found that all the S. aureus isolates were resistant to at least one antimicrobial. Most isolates (95.9%) were resistant to penicillin, with high resistance to ampicillin (82.7%) and multidrug resistance in 76.5% of cases. One isolate could simultaneously resist eleven antimicrobials (ERY-CLI-GEN-SMZ-FFC-PEN-PRL-AMC-CIP-TET-AMP). In contrast, all the isolates showed sensitivity to vancomycin. The most prevalent virulence gene was sed, accounting for 10.2%, followed by sec (8.2%). Regarding genetic polymorphism, these isolates were divided into 21 different sequence types (STs) using multilocus sequence typing (MLST) and 33 staphylococcal protein A (spa) types using spaTyper 1.0 tool. The most prevalent sequence types were ST398 (22.4%), followed by ST7 (20.4%), while ST59, ST1, ST188, ST9, ST398, and ST7 were observed in MRSA isolates. The most prevalent spa types were t034 (15.3%), followed by t899 (10.2%), while t441, t127, t184, t899, t034, and t091 were observed in MRSA isolates. In conclusion, our study highlights the high prevalence of S. aureus and MRSA in different retail raw meats in Shandong. This poses a potential threat to food safety and underscores the need for enhanced surveillance and stricter antibiotic control measures.