Detection of femA and mecA genes in Staphylococcus aureus isolated from bovine raw milk using duplex PCR and determination of the minimum inhibitory concentration of the isolates

Abstract

This study identified Staphylococcus aureus and the methicillin-resistant (MRSA) strains in raw milk samples using molecular methods, and their minimum inhibitory concentrations (MIC) were evaluated. Two hundred fifty-one samples of raw milk samples from bulk tanks, collected in the state of Minas Gerais, Brazil were analyzed using polymerase chain reaction (PCR) to investigate the presence of femA gene in 278 S.aureus isolates. Furthermore, MRSA strains were investigated for detecting mecA gene. All of 278 isolates contained the femA gene (132 bp), and in 11 samples (3.95 %) the mecA gene (533 bp) was identified. The minimum inhibitory concentration against S. aureus was determined using enrofloxacin, trimethoprim-sulfamethoxazole, gentamicin, azithromycin, tetracycline, cephalothin, amoxicillin, penicillin G and lincomycin. Enrofloxacin and trimethoprim-sulfamethoxazole showed to be the most effective inhibitors, as this study identified 149 of 161 isolates (92.5 % of susceptibility) with MIC≤ 4 mg/ mL, and 55 of 66 isolates (83.3 % of susceptibility) with MIC≤ 2 mg/mL, for the first antimicrobial drug and the second one, respectively.