Characterization of Staphylococcus aureus isolates from bovine mastitis in Ningxia, Western China

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.

PMID:33866044 | DOI:10.1016/j.jgar.2021.03.021