Molecular Characterization and Antibiogram Profiling of Methicillin- and β-Lactam-Resistant Staphylococcus aureus in Dogs with Respiratory Infections in Lahore, Pakistan

Methicillin and -lactam-resistant Staphylococcus aureus (S. aureus) are pathogens that prolong the respiratory infection in dogs and have major zoonosis concern for humans living in the vicinity of these infected animals.Overall, 384 nasal swab samples from dogs with respiratory tract infections were collected and processed for the confirmation of S. aureus, methicillin-resistant (MRSA), and -lactam-resistant S. aureus (BRSA) using phenotypic and molecular methods (PCR and sequencing).The results showed 38.02% prevalence of S. aureus, and among those, 43.15% and 50.00% isolates were approved as MRSA and BRSA on cefoxitin and penicillin disc diffusion test.PCR results confirmed 47.26% and 51.37% isolates as MRSA and BRSA, respectively.The mecA and blaZ gene sequences were submitted to NCBI, and accession numbers were attained, followed by the phylogenetic evaluation and in silico analysis of respective genes using bioinformatics tools.Phylogenetic analysis revealed genetic similarities with isolates from neighboring regions, suggesting crossboundary transmission, while in-silico analysis showed significant similarity of the isolated samples with reported 3D protein templates, and confirmed their conformational stability.Antimicrobial susceptibility of isolates revealed a higher resistance to commonly prescribed -lactams (penicillin, cefoxitin, amoxicillin, cephalosporins) and aminoglycosides, leaving doxycycline and fluoroquinolones as partially effective options.Risk factor analysis revealed various animal and management based variables to be significantly associated with staphylococcal respiratory infections.The findings suggested that the emergence of antimicrobialresistant S. aureus in dogs underscores a growing therapeutic challenge with potential zoonotic implications.