Detection of Methicillin-resistant Staphylococcus aureus Strains Isolated from Bovine Mastitis

The aim of present study was to investigate the antimicrobial resistance,and the prevalence of methicillin-resistant Staphylococcus aureus(S.aureus) isolated from bovine mastitis in Gansu province,to provide credible theory evidence for prevention and treatment on bovine mastitis.Eight commonly used antimicrobial agents were used for determining antimicrobial susceptibility of 17 total S.aureus strains by disk diffusion method.Agar screen method was used for determining the oxacillin and vancomycin minimum inhibitory concentration value as well.Disk diffusion method using the cephamycin antibiotics cefoxitin and detection of mecA gene by PCR assay were performed to detect the presence of MRSA.Most of strains showed a high resistance for penicillin and sulfafurazole,yet keeping complete sensitivity for ciprofloxacin,cefazolin,vancomycin and oxacillin.None MRSA isolate was identified by the phenotypic detection method,but eight MRSA isolates with the MIC of oxacillin lower than 2 μg/mL were found to carry mecA gene via PCR approach.This study suggested that the antimicrobial resistance of S.aureus of bovine origin was very serious.High frequency of mecA-positive oxacillin-susceptible S.aureus(OS-MRSA) were present in our herds.