Prevalence, characterization and antibiogram of Staphylococcus aureus isolates from bovine and swine population in Bareilly, Uttar Pradesh, India.

Livestock is an important agriculture sector in India and exhibits an indispensable part of economy of the country. The rising prevalence of Staphylococcus aureus (S. aureus), particularly methicillin-resistant (MRSA) and vancomycin-resistant (VRSA) strains, in livestock has become a significant concern in public health and veterinary medicine. S. aureus is a versatile pathogen capable of colonizing various animal species, leading to potential zoonotic transmission. This study aimed to assess the prevalence, biofilm formation, antimicrobial resistance (AMR), and molecular characterization of S. aureus isolates from cattle, buffalo, and pigs in Bareilly district, Uttar Pradesh, India. A total of 406 samples including 187 milk samples and 200 nasal swabs from apparently healthy animals and 19 wound swabs were collected from cattle, buffalo, and pigs. Isolation was performed using Brain Heart Infusion (BHI) broth enrichment followed by streaking on Mannitol Salt Agar (MSA). Biochemical and molecular tests were conducted to identify S. aureus, and the prevalence rates were calculated. PCR was used to confirm species identity and to detect biofilm-associated genes (icaA, icaD), as well as methicillin resistance genes (mecA, femA). Antimicrobial susceptibility was determined by the Kirby-Bauer disc diffusion method. The overall prevalence of S. aureus was 17.73%, with cattle exhibiting the highest prevalence (22.77%), followed by buffaloes (15.90%) and pigs (6.94%). Biofilm-associated genes were detected in 40.28% of isolates, and 20.83% and 13.89% of isolates were positive for the mecA and femA genes, respectively, indicating MRSA. Among the 72 S. aureus isolates, 62 (86.11%) were multidrug-resistant (MDR), with high resistance to streptomycin (80.56%) and β-lactams. Four isolates (5.55%) showed resistance to vancomycin, designated as VRSA. The prevalence of MRSA was 26.39% among the S. aureus isolates. The study highlights the significant prevalence of S. aureus and emerging multidrug-resistant strains, including MRSA and VRSA, in livestock in Bareilly district. These findings underscore the need for stringent antimicrobial stewardship and surveillance programs to prevent the spread of resistant strains, which pose both veterinary and public health risks. The presence of biofilm-forming isolates further complicates treatment and emphasizes the necessity for continued research and interventions to combat antimicrobial resistance in the agricultural sector.