Mapping Prevalence, Antimicrobial Resistance, and Biofilm Production of Dairy Farm Associated Coagulase-Positive Staphylococcus aureus From Punjab, India.

Antimicrobial-resistant Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), is an increasing concern in dairy production. Using a One Health approach, this cross-sectional study assessed the prevalence, antimicrobial resistance (AMR) profiles, and biofilm-forming ability of S. aureus from pooled bovine milk, animal handler hand swabs, and herd slurry collected from 405 farms across Punjab, India. The prevalence of coagulase-positive S. aureus was highest in hand swabs (43.7%), followed by milk (30.1%) and slurry (17.5%). Phenotypic resistance varied by source: milk isolates showed the greatest resistance to cefoxitin (37.7%) and penicillin (36.9%); hand swab isolates showed resistance to erythromycin (42.9%) and tetracycline (36.7%); and slurry isolates showed resistance to tetracycline (66.2%) and cefoxitin (59.2%). Multidrug resistance (MDR) was found in 45.9% of milk, 60.5% of hand swabs, and 92.9% of slurry isolates. MRSA was detected in 6.6% of milk, 2.8% of hand swab, and 1.4% of slurry isolates, with SCCmec type V as the most common type. Genotypic screening identified blaZ, mecA, tetK, ermC, and aacA-aphD, with the highest genotype-phenotype concordance for tetracycline resistance. Biofilm assays showed 94.9% of isolates formed biofilms; 28.4% were strong producers. MDR milk isolates showed the highest strong biofilm capacity (39.3%). This study underscores the need for integrated AMR surveillance and improved dairy biosecurity.