Molecular typing of Staphylococcus aureus isolated from bovine mastitis based on polymorphism of the coagulase gene in the north west of Iran

Abstract

The objective was to investigate the genotypic characteristics and distribution of Staphylococcus aureus in 9 dairy herds of Tabriz and Urmia regions which are located in east and west Azerbaijan provinces, respectively, Iran. In this study 58 S. aureus isolates were recovered from 370 milk samples of cows with clinical and subclinical mastitis. S. aureus isolates were identified on the basis of the cultural and biochemical properties as well as by amplification of the aroA gene specific to S. aureus and then were analyzed using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) of the coagulase gene (coa). Amplification of the variable region of the coa gene from these isolates produced five different PCR products ranging in size from approximately 490 bp to 850 bp. To obtain RFLP patterns of the PCR products they were subjected to digestion with restriction endonuclease HaeIII and the fragments separated by gel electrophoresis. Nine coa gene RFLP patterns, numbered I-IX, were observed, with 23 isolates (39.66%) assigned to RFLP pattern I and 14 isolates (24.14%) assigned to RFLP pattern III. Five out of nine patterns were found in both regions and four of nine patterns were only found in one region. The results demonstrated that several variants of the coa gene are present in the studied regions, but only a few of them were predominant, suggesting contagious transmission, a common source, or host adaptation of subset of the population of S. aureus strains. This study also indicated that genetic heterogeneity among S. aureus isolates recovered from bovine mastitis may be exists within and among herds in different regions.