Short communication: Detection and molecular characterization of methicillin-resistant Staphylococcus aureus isolated from subclinical bovine mastitis cases in China

摘要

This study investigated the antimicrobial susceptibilityof methicillin-resistant Staphylococcus aureus(MRSA) isolated from cases of subclinical bovine mastitisin China, as well as resistance mechanisms andvirulence genes encoding adhesins and toxins. Wedetermined antimicrobial susceptibility using the diskdiffusion method, and analyzed resistance, adhesin, andtoxin genes using PCR. We confirmed MRSA in 73 of498 (14.7%) Staph. Aureus isolates recovered from subclinicalmastitic milk samples. All isolates were positivefor mecA. The MRSA isolates showed high resistanceto penicillin (100.0%), gentamicin (100.0%), and tetracycline(98.6%). All MRSA isolates harbored resistancegenes blaZ (penicillin), aacA/aphD (gentamicin), andtetM (alone or in combination with tetK, tetracycline).Moreover, all isolates carried the adhesin genes fnbpA,clfA, clfB, can, sdrE, and map/eap, and most carriedsdrC (98.6%), sdrD (95.9%), bbp (94.5%), and ebpS(80.8%). The toxin genes she, hla, and hld were presentin all isolates, and most isolates carried sea (71.2%),seg (84.9%), sei (82.2%), lukE-lukD (97.3%), and hlg(72.6%). These findings of high-level resistance to antimicrobialscommonly used in dairy cattle should leadto calls for antibiogram analysis before antimicrobialtherapy. The high frequency of adhesin and toxin genesin MRSA indicates their potential virulence in bovinemastitis in China.