Evaluation of antibiotic resistance of Staphylococcus aureus isolated from bovine mastitis

Mastitis is one of the most important diseases in the livestock industry, which causes many economic losses. Staphylococcus aureus is one of the infectious agents of bovine mastitis. Due to the prevalence of antibiotic resistance in isolates of this bacterium, the aim of this study was to determine the antibiotic resistance pattern of bovine mastitis S. aureus isolates. This study was conducted in 7 industrial farms around Hamedan. The amount of 100 μl milk samples were cultured on the specific and differential culture media and according to the characteristics of S. aureus on these media, the bacteria were isolated. Isolated bacteria were confirmed by PCR test for genus and species specific gene (femA). Then, the antibiotic resistance patterns to different antibiotics were investigated by disk diffusion method and the results were reported according to the CLSI standard. In the present study, from a total of 280 milk samples taken from 7 industrial farms, a total of 53 (18.92%) S. aureus bacteria were isolated. Based on the results, the highest resistance was related to penicillin (100% resistant) and the highest sensitivity was related to the vancomycin (2 cases resistant (3.7%)). The results of this test showed that out of 53 bacteria, 7 (13.20%) had intermediate resistance to vancomycin. The report of high resistance to common antibiotics in this study is very important. Also, the observation of 7 cases of intermediate resistance and one case of complete resistance to vancomycin is a serious warning for the emergence of vancomycin-resistant animal strains.