Isolation, identification of Staphylococcus aureus from bovine milk and its antibiotics susceptibility

The isolation, identification of Staphylococcus aureus from bovine milk and its antibiotic susceptibility was studied. One milliliter of each freshly drawn milk sample was inoculated into 9 ml of sterile peptone water and incubated overnight. A loop full of peptone water broth was streaked on blood agar base enriched with sheep blood using the quadrant streaking method for each quarter. Blood agar plates were incubated aerobically at 37°C for 24 h. S. aureus was identified by the tube coagulase test. Antimicrobial sensitivity test was conducted on S. aureus isolates using 18 antibiotics. From the study 43.75% had subclinical mastitis, while none was tested positive for clinical mastitis. None of the S. aureus isolates was fully sensitive to all the agents; 3 (42.86%) isolates were resistant to 10 agents, followed by 2 (28.57%) isolates which were resistant to 4 agents.