Genetic relatedness, antibiogram and virulence factors of Staphylococcus aureus isolated from bovine mastitis and related human contacts.

The objectives of this study were to determine the genetic relatedness, antibiogram and virulence factors of Staphylococcus aureus (S. aureus) isolated from bovine mastitis, associated farm workers, dairy cow farm veterinarians (private veterinarians), veterinary students, and non-veterinary university students. A total of 84 S. aureus isolates (27 from mastitis, 11 from farm workers, 9 from private veterinarians, 22 from veterinary students, and 16 from non-veterinary university students) were used to determine antimicrobial sensitivity patterns using disk diffusion test, virulence factors using PCR technique and phylogenic analysis using pulsed field gel electrophoresis. All S. aureus isolates were resistant to 2 or more commonly used antibiotics. All isolates from mastitis, farm workers, and veterinary students carried the genes encoding coagulase and thermonuclease factors while isolates from non-veterinary university students carried the genes encoding coagulase, clumping, and thermonuclease factors. The mecA gene was detected in 22.2%, 81.8%, 100%, 95.5% and 100% of isolates from mastitis, farm workers, private veterinarians, veterinary students, and non-veterinary university students, respectively. In the phylogenic analysis, 10 (45.5%), 6 (66.7%) and 8 (72.7%) isolates from veterinary students, private veterinarians and farm workers, respectively were more than 80% similar to isolates from mastitis. Results of this study indicate that S. aureus isolates from mastitis milk and those from related dairy cow personnel and veterinarians share similar antimicrobial sensitivity patterns and virulence factors, therefore a common source of bacteria may exist. Furthermore, possible transmission of S. aureus between cows and cow-related personnel and vice versa could also exist.