Emergence of Methicillin-Resistant Staphylococcus aureus from Subclinical Mastitis of Cholistani Sheep Posing a Great Threat to the Development of Antibiotic Resistance

Mastitis is a serious illness that affects dairy sheep. All around the world, dairy farms have been shown to harbour methicillin-resistant S. aureus (MRSA). The study investigated the subclinical mastitis in sheep, associated risk factors, the presence of MRSA its susceptibility against different antibiotics. The positive milk samples were cultured for identification of Staphylococcus aureus on mannitol salt agar and confirmed through biochemical tests and Gram staining. MRSA was identified and confirmed by phenotypic method using oxacillin antibiotic discs through disc diffusion test. A data capture form was used for recording various assumed determinants related to subclinical mastitis in sheep. The study revealed that 12% (48/400) samples were positive for subclinical mastitis, and among these, a majority of the samples (88%, 42/48) were positive for S. aureus. Prevalence of MRSA based on disc diffusion test was 21.42% (9/42). Poor milker care during milking, unhygienic milking, high milk yield, use of teat dips, and mixed type of grazing were significantly (p<0.05) associated with subclinical mastitis in sheep mastitis. Results of in-vitro antibiotic susceptibility trials showed that MRSA was 100% resistance to Cefoxitin (30µg), 11.11% to Oxytetracycline (30µg) and Tylosin (30µg), 33.33% to Fusidic acid (10µg) and Vancomycin (30µg), 11.11% to ciprofloxacin (5µg) while it was sensitive to Moxifloxacin (5µg), Trimethoprim + Sulfamethoxazole (1.2µg, 23.75µg) and Linezolid (30µg). The study concluded that subclinical mastitis is an important issue in sheep, the presence of resistant isolate MRSA needs effective treatment to prevent its spread in lambs and humans to reduce antibiotic resistance issues