Characterisation of methicillin-susceptible Staphylococcus pseudintermedius isolates from canine infections and determination of virulence factors using multiplex PCR

Staphylococcus pseudintermedius is a genuine opportunistic pathogen of the skin, especially in canids. However, characterisation of virulence, antimicrobial resistance and genotypic variability in methicillin-susceptible S. pseudintermedius isolates has not been fully explored. In this study, coagulase-positive staphylococcal isolates collected from dogs of various breeds and ages suffering from dermatitis (n = 70), pyoderma (n = 7), and otitis (n = 7), from districts of Prague (Czech Republic) and surrounding areas, were characterised using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, and repetitive sequence-based PCR fingerprinting. Susceptibility to antimicrobial agents was determined, virulence factor genes for leukocidin (lukSF-I), exfoliatins (exi, expB, and siet), enterotoxin C (sec(canine)) and enterotoxin-related genes (se-int and sel) were detected using multiplex PCR and the genotypes of S. pseudintermedius isolates were determined using SmaI macrorestriction analysis. The majority of the staphylococcal isolates (n = 84) were identified as S. pseudintermedius (n = 79) and all of them were susceptible to methicillin/oxacillin (MSSP). About half of the strains (n = 41) were resistant to macrolide-lincosamide-streptogramin B antimicrobial agents and resistance was mediated in all but one of the strains by the erm(B) gene. The genes for lukSF-I, siet, se-int, and sel were detected in the majority of the MSSP strains (96.2%, 100%, 100%, and 73.4%, respectively). Investigated canine S. pseudintermedius isolates were highly heterogeneous, which prevented the correlation of any specific lineage to a particular infection, dog breed, or region of origin.