Prevalence and antimicrobial resistance characterization of multidrug-resistant Staphylococcus epidermidis isolated from raw milk of dairy cattle and ewes

The study investigated the occurrence of subclinical mastitis (SCM) and the presence of multidrug-resistant (MDR) Staphylococcus epidermidis in raw milk from cattle and ewes in Pakistan. In 310 milk samples, SCM was found in 26% of cases overall (31.34% in ewes vs. 21.87% in cattle). S. epidermidis was detected in 12.9% of samples, with 72.5% of these isolates coming from SCM-affected animals. Among the S. epidermidis isolates, 95% were resistant to penicillin and erythromycin, with much lower resistance to levofloxacin and ciprofloxacin (5%). Half of the isolates qualified as MDR (resistant to three or more antibiotic classes). Gene screening revealed high prevalence of ermC (87.5%) and tetK (80%) resistance genes, and 45% carried the mecA gene. The findings underscore the dual role of S. epidermidis as both a commensal and potential pathogen in dairy animals, and raise concerns for antibiotic-resistance management in food-animal systems.