Antimicrobial Resistance Profiles and Virulence Gene Characterisation of Staphylococcus aureus from Bovine Mastitis in Kaduna State

This study characterises the antimicrobial resistance profiles and virulence determinants of Staphylococcus aureus isolated from bovine mastitis cases in Kaduna State, located in Nigeria's North West geopolitical zone. Bovine mastitis caused by Staphylococcus aureus is a persistent challenge in dairy production, and understanding resistance profiles and virulence gene carriage is essential for designing effective treatment protocols and assessing public health risks from this zoonotic pathogen. Using a cross-sectional design, milk samples were collected from 240 clinical and subclinical mastitis cases on 40 dairy farms across three agricultural zones in Kaduna State. Staphylococcus aureus was isolated by standard bacteriological methods, confirmed by coagulase testing and PCR for the nuc gene. Antibiotic susceptibility testing was performed by disc diffusion using CLSI guidelines. Multiplex PCR was used to screen isolates for virulence genes encoding enterotoxins (sea to see), haemolysin (hla), and biofilm-associated genes (icaA, icaD). Methicillin resistance was confirmed by mecA gene PCR. The study fills a critical research gap by providing the first comprehensive virulence gene profile of bovine Staphylococcus aureus from Kaduna State. Findings revealed multidrug resistance in 52 percent of isolates, mecA-mediated methicillin resistance in 14 percent, and enterotoxin gene carriage in 38 percent, highlighting significant zoonotic implications. Keywords: Staphylococcus aureus, mastitis, antimicrobial resistance, virulence genes, Kaduna State.