Investigation of the presence of methicillin resistant Staphylococcus aure-us (MRSA) carrying different mec types in isolates causing bovine sub-clinical mastitis

Staphylococcus aureus is one of the most important agents causing mastitis in dairy cattle. The emergence of methicillin resistance in S. aureus is a concern in veterinary medicine and public health. Due to the identification of new types of genes encoding methicillin resistance in recent years, the aim of this study was to investigate the presence of methicillin resistant (MRSA) and types of mec gene for the first time in the northeast of Iran. In the present study, the identity of 54 staphylococcus aureus isolates causing bovine subclinical mastitis were investigated using biochemical and molecular tests. Among them, the species-specific nuc gene was detected in 44 strains. Then, resistance of isolates to penicillin, cefoxitin, enrofloxacin, tylosin and trimethoprim-sulfamethoxazole were determined using the disk diffusion method. Finally, the molecular investigations for detection of the mecA, mecC, mecB genes were conducted. According to the results, the highest resistance were related to penicillin (54%) and trimethoprim-sulfamethoxazole (23%), and the lowest resistance was related to taylosin (7%). The mecA gene was observed in only one isolate (2.3%), while the isolate was not identified as MRSA in phenotypic test. The results of the present study show that the incidence of methicillin resistance in bovine mastitis strains of the area is not high. This study also showed that less known types of mec genes were not common in this region. However, further studies must be perform in this regard.