Prevalence and risk factors of methicillin-resistant Staphylococcus aureus in raw cow’s milk and nasal and hand swabs of milkers in dairy farms in Mekelle city, Northern Ethiopia

BACKGROUND: Staphylococcus aureus causes subclinical mastitis in dairy cows, leading to severe economic losses. Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for over 70,000 severe human infections and 9,000 deaths per year in the United States, with anticipated even higher rates in the African region. MRSA causes many infections, including skin & wound infections, pneumonia, and bacteremia in humans. In animals, it is commonly associated with mastitis. Therefore, the study aimed to determine the prevalence of methicillin-resistant S. aureus and associated factors from raw milk of lactating cows, and nasal and hand swabs of milking persons in selected dairy farms in Mekelle City, Northern Ethiopia, from a one-health perspective. METHODS AND MATERIALS: A cross-sectional study was conducted in 180 selected dairy farms in Mekelle, from December 2024 to May 2025. Background information about the dairy farms, lactating cows and milking personnel was collected using a structured questionnaire. Raw milk, hand swabs, and nasal swabs were cultured on Mannitol salt agar, and identification of S. aureus was done following standard procedures. The antimicrobial susceptibility testing and MRSA screening were performed based on the Clinical Laboratory Standards Institute’s recommendations. A logistic regression model was applied to measure the association between variables using SPSS version 27. A significant association between the independent and dependent variables was declared at p < 0.05 and a corresponding 95% confidence interval. RESULTS: The prevalence of S. aureus from raw milk, nasal swabs and hand swabs of milking persons was 17.2%, 18.9% and 15.6%, respectively. The prevalence of MRSA in lactating cows and milking persons was 2.2% (4/180) and 2.8% (5/180), respectively. The prevalence of S. aureus and MRSA among the California mastitis test (CMT) positive lactating cows were 54.4% and 7% respectively. Among the S. aureus isolates, 19.4%, 17.6% and 10.7% were MDR from raw milk, nasal and hand swab samples, respectively. MRSA positivity in humans and a history of hand lesions in milking persons were significantly associated. CONCLUSION: The study revealed a high burden of MDR MRSA strains both in lactating cows and milking persons, implication the importance of one health tailored mitigation measures in the region.