Identification and Typing of Staphylococcus aureus Isolated from Clinical Bovine Mastitis in Sanandaj City Using PCR-RFLP Analysis of the aroA Gene

Staphylococcus aureus is one of the most important causes of contagious mastitis in domestic animals. Due to the existence of multiple strains of S. aureus and strain variations in chromosomal allelic rearrangement, different genotyping methods, such as analysis of the chromosomal DNA following the enzymatic digestion, are introduced for genetic typing of the bacterium. In the present survey, for the first time, the genetic diversity of S. aureus recovered from clinical bovine mastitis in Sanandaj was investigated based on PCR-RFLP analysis of the aroA gene. 120 bovine mastitic milk samples were collected aseptically and assessed. S. aureus isolated in culture and routine bacteriological methods were analyzed by aroA gene-based PCR. The amplicons with a size of 1153bp were digested with TaqI restriction enzyme and the fragments were electrophoresed. 28 S. aureus strains were isolated in phenotypic method among which the expected amplicon was observed in all of them. In enzymatic digestion, two RFLP patterns, nomenclatural based on the previous studies were generated. Genotype B was detected in 23 (82.14%) isolates and genotype N in 5 isolates (17.85%). The results demonstrate that S. aureus is involved in bovine mastitis in Sanandaj and despite the presence of limited genotypes, strain variation of this bacterium exist in the region. The presence of genotype B in all farms implies the same source of infection among farms, which should be considered in control programs of mastitis. Non-detection of universal genotype A and specific genotype of the bacterium in Sanandaj is reported for the first time.