Antimicrobial resistance and epidemiological determinants of single and polymicrobial staphylococcal infections in...

Canine pyoderma is a common bacterial skin infection predominantly caused by Staphylococcus species. This study, conducted from June to December 2024, analysed 71 PCR-confirmed cases of staphylococcal pyoderma to investigate epidemiological and host-associated risk factors and antimicrobial resistance (AMR) patterns. Bacterial isolates from PCR-positive samples were identified using MALDI-TOF MS and tested for antimicrobial susceptibility. Of the cases analysed, 63.38% involved monomicrobial infections, whereas 36.62% were accounted for polymicrobial infections. Staphylococcus pseudintermedius and Staphylococcus aureus were the predominant pathogens in both infection types, occurring alone or in combination with Escherichia coli, Pseudomonas aeruginosa or Klebsiella pneumoniae. Polymicrobial infections were significantly associated with recurrent disease, longer disease duration, tissue invasion and allergic skin manifestations. Both major Staphylococcus species exhibited high resistance to β-lactams and third-generation cephalosporins, with notable interspecies differences in resistance to ceftizoxime, trimethoprim-sulfonamide, amikacin, enrofloxacin and clindamycin. Although overall AMR did not differ significantly between major staphylococci species associated to monomicrobial and polymicrobial infections, however isolates from polymicrobial cases showed a consistent trend toward higher resistance across multiple antimicrobial classes. The findings emphasise the complexity of canine pyoderma characterised by bacterial communities dominated by Staphylococcus pseudintermedius and the increasingly relevant Staphylococcus aureus with potential zoonotic implications. Routine species-level identification, culture-guided therapy and continuous AMR surveillance are crucial for effective treatment and antimicrobial stewardship within a One Health framework.