Staphylococcus aureus and Staphylococcus pseudintermedius isolated from humans and pets - a comparison of drug resistance and risk factors associated with colonisation.

Introduction: Staphylococci commonly colonise the skin and mucous membranes of humans and animals, the close contact between which may promote interspecies transmission of these microorganisms and determinants of drug resistance.

Material and methods: Material collected from animals (n = 274) and humans (n = 261) between 2019 and 2023 was studied. Samples were swabbed from six anatomical sites of each pet: the external ear canal, conjunctival sacs, nares, oral cavity, groin skin and anus. Swabs were taken from four places of each human: the vestibule of the nasal cavity, the throat near the tonsils, and the skin behind the auricle and in the elbow bend. The pets' owners and the human participants completed a questionnaire about the study subject and the subject's living environment to elucidate risk factors associated with staphylococci colonisation.

Results: The prevalence of Staphylococcus aureus was 12.42% in cats and 8.85% in dogs, while S. pseudintermedius was isolated from 5.59% of cats and 58.41% of dogs. Of the people, 38.7% were carriers of S. aureus and 2.68% carriers of S. pseudintermedius. A total of 202 S. aureus strains and 165 S. pseudintermedius strains were analysed. Drug resistance was tested in disc diffusion and resistance genes were detected by PCR. The most frequent resistance of S.aureus was to ampicillin (62.4%), penicillin (61.4%) and erythromycin (29.2%), while S. pseudintermedius was mostly resistant to penicillin (71.5%), ampicillin (63.6%) and clindamycin and erythromycin (41.2% in both cases). Methicillin resistance was found in 4.5% of S. aureus and 12.1% of S. pseudintermedius isolates. The most common S. aureus resistance genes were blaZ (79.7%), tet[M] (53.1%) and ermA (29.7%) and the S. pseudintermedius pattern was of blaZ (84.2%), tet[M] (53.3%) and ermB (38.2%). Regarding risk factors, animals from non-commercial sources had 11-fold higher methicillin resistance than those from commercial breeders, dogs had 50-fold lower risk than humans, and recent antibiotic treatment also increased resistance.

Conclusion: Monitoring the epidemiology of strains and knowing the prevalence of resistant isolates can shape preventive programmes in both veterinary and human medicine, inform appropriate therapeutic decisions and combat the phenomenon of drug resistance.