Abstract:[Objective] To investigate the prevalence, antimicrobial susceptibility, and genetic characteristics of Staphylococcus aureus from ready-to-eat foods (stewed meat, roast, salad and pasteurized milk) and vegetables from 15 representative cities of China and to provide baseline information for effective tracing S. aureus source and controlling food contamination.[Methods] All samples were subjected to qualitative and most probable number (MPN) analysis for S. aureus according to the National Food Safety Standard-Food microbiological examination:S. aureus. Antimicrobial susceptibility of all isolates was evaluated using the Kirbye-Bauer disk diffusion and mecA-positive isolates was obtained by PCR. The sequence types of S. aureus were performed via multilocus sequence typing (MLST).[Results] In total 540 food samples, 9.3% (50/540) were tested positive for S. aureus, of which the most polluted foods were stewed meat (16.3%, 30/184) followed by roast (9.2%, 6/65), and vegetable showed lowest prevalence (4.0%, 6/150). Most probable number (MPN) analysis showed that 62.0% samples were ranged from 0.3 to 1 MPN/g, and three samples exceeded 110 MPN/g. 82.0% isolates were resistant to ampicillin and penicillin G, and 64.0% isolates were multi-drug resistant. In addition, the mecA-positive isolates were both belonged to the SCCmecIVa subtype using staphylococcal cassette chromosome mec (SCCmec) typing. Furthermore, 14 sequence types (STs) were obtained by MLST, including two novel STs (ST3595 and ST3847).[Conclusion] The general multi-drug resistance exhibited by S. aureus was still the most serious issue of common concern, which posing a health risk for consumers. In addition, the antimicrobial susceptibility of S. aureus was highly associated with STs. Therefore, it is necessary to provides scientific data for further analysis of epidemic trends and risk assessment of bacteria prevalent in foods.
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