J Glob Antimicrob Resist. 2021 Apr 15:S2213-7165(21)00088-6. doi: 10.1016/j.jgar.2021.03.021. Online ahead of print.
OBJECTIVES: The aim of this study was to explore the antimicrobial resistance, virulence genes, and molecular characteristics of S. aureus from bovine mastitis cases.
METHODS: Here, we characterized 125 non-duplicate S. aureus isolates from bovine mastitis cases, antimicrobial susceptibility testing and molecular testing were conducted to determine the antimicrobial resistance, virulence genes and molecular characteristics.
RESULTS: All MRSA isolates were resistant to ampicillin, oxacillin, ceftiofur, erythromycin, gentamicin, and clindamycin, with resistance to nine different categories of antibiotics observed amongst the MRSA isolates, 62.1% of the MSSA isolates were resistant to ampicillin and sulfisoxazole. In this study, 9 clonal complexes and 16 spa types were identified by MLST-genotyping and spa typing. The dominant CCs were CC97 (51.2%) and CC50 (30.4%), while t224 (30.4%), t518 (20%), and t359 (16.8%) were the most common spa types. A relative high proportion (27.2%) of the S. aureus isolates belonging to ST4053, a novel sequence type identified in the current study. In addition, two CC30 MSSA isolates and two CC59 MRSA isolates were positive for Panton-Valentine leucocidin, while one CC239 MRSA isolate and three CC5 MSSA isolates were positive for TSST-1. All MRSA isolates carried the IEC genes and included scn (100%, 9/9) and sak (100%, 9/9), which were classified into type E.
CONCLUSIONS: Our study indicates severe antibiotic resistance and complicated molecular characterization of S. aureus causing bovine mastitis, additional studies should be conducted to monitor the infection and transmission of S. aureus.