Occurrence of mecA-Carrying MRSA within the Bovine Milk Chain of Eastern Uttar Pradesh

Milk is considered as whole food that contains essential nutrients, making it and its products food item a popular globally. The global milk production is estimated to be around 992.7 million metric tons in 2025, with India being one of the largest milk producers, accounting for approximately 25 % of the world's total milk production. In 2023-24, India produced over 239.30 million metric tons of milk, with Uttar Pradesh (37.46 million metric tons), Rajasthan (31.6 million metric tons), Gujarat (17.281 million metric tons) Punjab (13.64 million metric tons) and Haryana (11.53 million metric tons) being the leading milk-producing states.The dairy industry significantly contributes the Indian economy not only to employment generation but also accounting for around 5% of the country's GDP. In Asia, mastitis can be caused by a range of organisms, including bacteria, fungi and algae. The primary bacterial pathogens responsible for mastitis include S.aureus, S. agalactiae, E. coli, S. uberis, Klebsiella spp., Mycoplasma spp., C. bovis, T.pyogenes, P.aeruginosa, Yeasts and Molds. In India the prevalence of bovine mastitis due to S.aureus is around 40- 52 %. The present study aimed to determine the occurrence of mecA-carrying MRSA in the bovine milk chain of Eastern Uttar Pradesh. A total of 200 milk samples were collected from cattle and buffaloes. Isolation and identification of S. aureus were carried out using Mannitol Salt Agar, biochemical tests and PCR targeting the nuc gene. MRSA was screened using oxacillin-supplemented media, cefoxitin and oxacillin disc diffusion tests, and confirmed by detection of the mecA gene. Antimicrobial susceptibility testing and vancomycin MIC determination were also performed. Out of 200 samples, 130 (65.0%) were confirmed as S. aureus, of which 107 (53.50%) were identified as MRSA, with higher prevalence in mastitic milk. All MRSA isolates showed 100% resistance to methicillin, cefoxitin and ampicillin, while moderate resistance was observed against erythromycin, chloramphenicol and fluoroquinolones. The MAR index ranged from 0.25–0.917. Vancomycin MIC revealed 20.56% intermediate and 15.89% resistant isolates. The mecA gene was detected in 74.07% of phenotypically confirmed MRSA isolates.