Antimicrobial resistance, virulence factors, and molecular characterization of methicillin-resistant Staphylococcus aureus isolates cultured from ready-to-eat foods

Abstract

To understand the antimicrobial resistance, virulence factors, and molecular characterization of MRSA isolates cultured from ready-to-eat(RTE) foods from several provinces in China. Totally, 397 S. aureus isolates were collected from RTE foods from several provinces in China, in 2017. The mecA gene was amplified to detect the MRSA strains among all 397 isolates by a polymerase chain reaction(PCR) method. Furthermore, the antimicrobial susceptibility and virulence factors of the MRSA isolates were detected by broth microdilution method and PCR, respectively, while the molecular characterization of all MRSA isolates were analyzed by pulsed-field gel electrophoresis(PFGE). In total, 32 MRSA isolates were identified from 397 isolates. All 32 MRSA isolates were resistant to penicillin, oxacillin and cefoxitin. Meanwhile, 78. 1%, 65. 6%, 53. 1, 28. 1% and 12. 5% of the 32 MRSA isolates showed resistant to erythromycin, clindamycin, tetracycline, chloramphenicol, and ciprofloxacin, respectively. Resistance rates to gentamicin and trimethoprim-sulfamethoxazole of all MRSA isolates were less than 10%. Eleven drug resistant spectrums were identified and 29 out of 32 MRSA isolates were identified as multi-drug resistant(MDR) isolates and two isolates were found to resistant to 9 antimicrobial agents tested in this study. Of all, 27 MRSA isolates were detected to harboring 13 virulence genes with sel-q(56. 3%), sel-k(43. 8%), seb(28. 1%) and sec(18. 8%) genes being the top four frequently detected. Besides, the result also showed that two or more virulence genes could be detected in one MRSA isolate. Finally, all 32 MRSA were identified to have 26 PFGE patterns and no dominant PFGE patterns were found in this study. An overall high level antimicrobial resistance was found among RTE associated MRSA in China in 2017, so was the MDR condition. Virulence genes could be frequently detected in RTE associated MRSA isolates. The PFGE patterns of RTE associated MRSA showed wide distribution characteristics.