PREVALENCE OF STAPHYLCOCCUS AUREUS IN RAW MILK: CAN IT BE A POTENTIAL PUBLIC HEALTH THREAT?

Background:Staphylococcus aureus is important milk borne pathogen and causes a wide variety of diseases in humans and animals and it is frequently associated with subclinical mastitis in dairy animals and may contaminate milk and other dairy products which act as vehicles for S. aureus infection in humans. Aim: The present study was aimed to identify the prevalence of S. aureus in raw milk samples from small holder dairy units in Chennai city and to relate the results with public health implication of the infection levels in dairy animals and the milk. Methodology: A total of 100 individual raw milk samples (50 cows, 10 buffaloes, 40 goats) were collected. Standard protocol was followed for the isolation of S. aureus from milk in Baird Parker Agar with 2% egg yolk tellurite emulsion. Colonies suggestive for S. aureus (black surrounded by white halo) were submitted for the morphological characteristics by Gram’s staining and biochemical tests such as catalase and coagulase tests for confirmation. The positive presumptive isolates were further confirmed by Polymerase Chain Reaction (PCR) by targeting Nuc gene. Results: The overall prevalence rate of S. aureus in milk samples based on conventional techniques was 61 per cent (cow’s milk 68%, goat’s milk 62.5% and buffaloes milk 40%) and 65.57% S. aureus presumptive isolates were positive by PCR which includes 73.53 % of cow’s milk, 52 % of goat’s milk and 50% of buffaloes milk. Conclusion: In this study examined raw milk samples contains S. aureus indicates a potential route of S. aureus transmission may occur to consumers via contaminated milk or through contaminated dairy products. Hence, to improve the quality of milk and to prevent S. aureus contamination more hygienic preventive measures should be implemented.