Raw milk as a reservoir: Exploring the drug resistance profile of Staphylococcus aureus

Introduction: Staphylococcus aureus is a significant food-borne pathogen commonly found in raw milk and has growing public health relevance due to its increasing antibiotic resistance. Especially, MRSA is recognized as a priority pathogen globally and in India, with increasingly resistant complicated treatment efforts. This study aimed to isolate from raw milk samples using Mannitol Salt Agar (MSA) and assess their antimicrobial susceptibility to evaluate potential health risks. 
Materials and Methods: Raw milk samples were collected from local dairies in Ahmedabad and processed by serial dilution, then cultured on MSA and repeatedly subcultured to obtain pure colonies. Isolates were tested against antibiotics—Amoxicillin, Ampicillin, Azithromycin, Cefexime, Cefpodoxime, Kanamycin, Streptomycin, and Vancomycin. 
Results: Variable resistance patterns were observed, with specific isolates showing reduced sensitivity or complete resistance to β-lactam antibiotics such as Azithromycin and Vancomycin. At the same time, Amoxicillin and Kanamycin remained largely effective. The presence of resistant S. aureus in unpasteurized milk underscores the importance of adhering to stringent hygiene practices during milk production and of prudent antibiotic use in dairy farming to ensure food safety and public health. 
Conclusion: The source of many multi-drug-resistant S. aureus strains, including MRSA, might be zoonotically transmitted to consumers. Constant monitoring and targeted strategies should be applied in the dairy sector, given the practice of raw milk consumption in many rural areas of the world. Promoting hygienic milking procedures and farming practices, as well as encouraging milk pasteurization, is necessary to reduce the risks of microbial transfer and their associated public health implications.