OBJECTIVES:Staphylococcus pseudintermedius is the primary pathogen that causes pyoderma in companion animals. The increasing number of multidrug-resistant strains, including methicillin-resistant S. pseudintermedius (MRSP), has become a major concern, highlighting the need for comprehensive data on antimicrobial susceptibility. Furthermore, with advancements in the accurate identification of S. pseudintermedius in human clinical patients, it is imperative to elucidate its definitive zoonotic potential.
METHODS:We analyzed 111 strains of S. pseudintermedius derived from companion animals and 21 strains of S. pseudintermedius from human clinical patients to clarify antimicrobial susceptibility and correlation between strains derived from companion animals and humans.
RESULTS:Approximately half of the animal-derived S. pseudintermedius isolates were MRSP. The isolates, particularly MRSP, exhibited high resistance to multiple antimicrobials used to treat pyoderma. Although florfenicol and fusidic acid are not approved for the treatment of pyoderma in companion animals in Japan, their efficacy has been demonstrated. Genetic analysis revealed that ST121, ST45, and ST71 were the most common ST types in animals. Additionally, ten novel STs were identified. ST45 and ST71 have frequently been identified in companion animals abroad, suggesting potential international transmission. However, ST121 has rarely been reported outside Japan, indicating its unique evolutionary trajectory within the country. Furthermore, these sequence types were identified in strains isolated from humans. Core genome analysis revealed nearly identical genotypes, suggesting transmission from companion animals to humans.
CONCLUSION:A limited number of approved antimicrobials are effective against S. pseudintermedius (particularly MRSP), which is being transmitted as a zoonotic infection from companion animals to humans.