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STAPHYLOCOCCUS AUREUS in DAIRY ANIMALS and FARM WORKERS in a CLOSED HERD in KARNAL, NORTH INDIA: ASSESSMENT of PREVALENCE RATE and COA VARIATIONS

Purba Sarkar , Debasish Mohanta, Sachinandan De, Chanchal Debnath

In order to isolate and characterize S. aureus from milk of dairy animals and nasal swabs of farm workers, the present study was conducted on a total of 200 milk samples from lactating animals (including 50 Murrah buffaloes, 90 indigenous Sahiwal and 60 crossbred Karan Fries cattle) and 50 nasal swabs of farm workers in an organized dairy farm in Karnal, North India. The collected samples were cultured on mannitol salt agar and presumptive S. aureus colonies were confirmed phenotypically (coagulase, catalase and indole test) and genotypically (PCR amplification of nuc gene). Genotypic variation among S. aureus isolates from different sources was studied by amplifying the 3’ hypervariable region of the coagulase gene. 73.6% of all the samples, 74.5% of the milk and 70% of the nasal swabs were tested positive. Highest prevalence rate was observed in milk from crossbred cattle (88.33%) followed by indigenous cattle (80%) and buffalo (48%). 89.74% of previously treated animals and 53.01% of the healthy animals were tested positive. Amplification of the coagulase gene from the milk isolates produced a single PCR product of 600- bp whereas the nasal swab isolates produced five different PCR products of sizes 600 (10 isolates), 680 (14 isolates), 790 (8 isolates), 950 (1 isolate) and 1000-bp (1 isolate). Absence of variation among the milk isolates shows the importance of maintaining a close herd to prevent the entry of new S. aureus strains in the herd. However, the common existence of 600-bp genotype indicates transmission of the isolates between the species.