Genotyping of Staphylococcus aureus isolated from bovine mastitis based on PCR-RFLP analysis of the aroA gene

Abstract

The aim of this study was the genotypical characterization of 58 Staphylococcus aureus isolates from nine dairy herds in the Tabriz and Urmia regions of east and west Azerbaijan provinces, Iran. In this study, 58 S. aureus isolates from 370 milk samples from cows with clinical and subclinical mastitis were analyzed by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) analysis of the aroA gene. Amplification of the aroA gene resulted in a single amplicon with a size of approximately 1,153 bp from all 58 isolates of S. aureus. To obtain the RFLP patterns of the isolates, the PCR products were digested with TaqI restriction enzyme and the fragments separated by gel electrophoresis. Four distinct RFLP patterns were observed among the studied isolates. Three out of four detected genotypes had the same RFLP patterns (A, B, and N) as reported by previous studies. The fourth newly detected genotype in this study was named H. Genotypes A and B were the most frequent, being observed in 24 (41.38%) and 29 (50%) isolates, respectively. Genotypes N and H comprised 1.7% and 6.9% of all isolates, respectively. With the exception of the RFLP pattern N, which was observed only in the Tabriz region, all other patterns were found in both Tabriz and Urmia regions. The results demonstrate that strain variations of S. aureus could occur within and between herds and also between different regions, although a few genotypes of S. aureus were predominant in bovine mastitis. This study also indicated that PCR amplification of the aroA gene is specific for S. aureus identification.