Prevalence, Molecular Characterization and Antibiotic Resistance Profile of Staphylococcus aureus in Mastitis-Infected Dairy Cattle in Punjab, Pakistan

Abstract

Mastitis is considered one of the most widespread bovine infections, affecting dairy herds with the prevalence varying globally. The following research was conducted to isolate and characterize Staphylococcus aureus from milk samples from mastitis-infected cows in major dairy-producing regions of Central Punjab, Pakistan. A total of 210 raw milk samples were aseptically collected from five regions: Sahiwal (n=48), Gujrat (n=40), Sargodha (n=42), Faisalabad (n=54), and Mandi Bahauddin (n=26). The isolates were recovered and identified by phenotypic, biochemical, and molecular tests. Antimicrobial susceptibility test (AST) was determined using the Kirby–Bauer disc diffusion method as per Clinical and Laboratory Standards Institute guidelines (CLSI).   Among 210 milk samples, 38 (18.1%) were positive for S. aureus. The highest prevalence was recorded in Sahiwal (22.9%), followed by Sargodha (19.04%) and Gujrat (17.5%), while the lowest prevalence was found in Mandi Bahauddin (7.7%). AST showed high resistance to Penicillin G (79%), Azithromycin (47%), Erythromycin (45%), Ciprofloxacin (45%), and Trimethoprim/Sulfamethoxazole (39%). Conversely, Chloramphenicol (21%), Cefoxitin (26%), and Doxycycline (26%) showed lower resistance rates. In conclusion, this study highlights the presence of antibiotic-resistant S. aureus in raw milk samples from Punjab, Pakistan, and outlines the necessity of regular surveillance and conscious antibiotic use to manage this economically significant disease.