Nationwide surveillance and molecular characterization of methicillin-resistant Staphylococcus pseudintermedius isolated from dogs and cats in South Korea

Staphylococcus pseudintermedius is an important opportunistic pathogen of companion animals, mainly associated with skin and mucous membrane colonization among pets. We aimed to characterize the S. pseudintermedius isolates collected from dogs and cats nationwide in South Korea. A total of 1,071 S. pseudintermedius isolates were recovered from mostly dogs (n = 1037) and cats (n = 34) in four different infection sites: skin/ear (n = 887), urine (n = 28), respiratory tract (n = 49), and genital organs (n = 107). S. pseudintermedius isolates exhibited high resistance (> 50%) to penicillin, erythromycin, clindamycin, trimethoprim/sulfamethoxazole, and chloramphenicol. Antimicrobial resistance rates were significantly higher in non-skin isolates than in skin isolates from dogs (p < 0.05). In addition, the isolates demonstrated higher resistance to most antimicrobials in dogs of older ages. Multidrug resistance was detected in more than 70% of isolates. The methicillin resistance was detected in 35.1% of S. pseudintermedius. Furthermore, the methicillin-resistant S. pseudintermedius (MRSP) isolates showed significantly higher resistance to non-beta-lactam antimicrobials than the methicillin-sensitive S. pseudintermedius (MSSP) isolates (p < 0.05). Multi-locus sequence typing revealed the presence of 48 sequence types (STs) in 100 MRSPs, of which 24 types were identified newly in this study. The most frequently detected STs were ST121, ST794, ST1328, ST71, and ST496, comprising 33.3%. pRE25-like elements, including rec, IS1252, and IS1216, were identified in 62% of MRSP, commonly showing resistance to chloramphenicol. Moreover, the pRE25-like elements were associated with STs, with five predominantly detected STs carrying pRE25-like elements, except for ST71. The occurrence of methicillin resistance among S. pseudintermedius with predominant STs and pRE25-like elements in dogs and cats potentially poses health hazards to humans.