author(s)
K Manimaran, S Balakrishnan, A Sangeetha, Atmakur Venkatesh, M Dhanalakshmi and T Sivakumar

abstract
Staphylococcus aureus is an opportunistic contagious pathogen that causes clinical or subclinical mastitis in dairy cows throughout the world. It also has the potential to contaminate animal products during processing, preparation and storage. Injudicious use of antibiotics had led to the emergence of multi drug resistant strains, particularly Methicillin-resistant S. aureus (MRSA). The present study was conducted to investigate the prevalence of MRSA in dairy cows with clinical and sub-clinical mastitis brought to the Veterinary Clinical Complex, Veterinary College and Research Institute, Orathanadu. Milk samples were collected in sterile containers from 35 cows with mastitis for isolation, identification and antibiogram of S. aureus. Briefly, the collected milk samples were enriched in nutrient broth and a loopful of inoculum from enrichment broth was streaked onto Mannitol salt agar (MSA) and incubated at 37 °C for 24 h. The characteristic golden yellow coloured colonies observed on MSA was confirmed by Gram’s staining, biochemical tests such as IMViC, oxidase and catalase tests, PCR for nucA gene (279 bp) of S. aureus and subjected to Methicillin sensitivity pattern. S. aureus was isolated and confirmed from 40% of the samples and all the isolates were resistant to Methicillin (100%). Thus, the high prevalence of Methicillin resistant S. aureus mastitis is an important concern for diary industry and this an alarming concern for both animal and human beings on public health point of view, since the strains of this pathogen is becoming more resistant to commercially available antimicrobials.