Nationwide analysis of methicillin-resistant staphylococci in cats and dogs: resistance patterns and geographic distribution

OBJECTIVE: This study aims to quantify the frequency and resistance patterns of 3 methicillin-resistant staphylococci (MRS), Staphylococcus aureus (MRSA), Staphylococcus pseudintermedius (MRSP), and Staphylococcus schleiferi (MRSS), in companion animals, using historical culture and susceptibility data from a national diagnostic laboratory. METHODS: Samples from cats and dogs across the US, between 2019 and 2022, were analyzed. Methicillin-resistant isolates identified according to Clinical and Laboratory Standards Institute VET01S (5th ed) were included. Data included location, patient species, sampling site, year, and susceptibility results for various panels of antimicrobials. RESULTS: There were 110,423 MRSP, 5,618 MRSA, and 20,934 MRSS isolates identified. Methicillin-resistant S pseudintermedius was predominantly found in dogs (96.2%), with skin and soft tissue being the most common sites. Methicillin-resistant S aureus and MRSS were also primarily isolated from dogs, with significant yearly, regional, and species-specific differences in antimicrobial susceptibility observed. This study highlights high resistance levels in MRSP isolates, while MRSA and MRSS showed relatively higher susceptibility to several antimicrobials. CONCLUSIONS: This study provides insight into the distribution and antimicrobial resistance patterns of MRSA, MRSP, and MRSS in companion animals in the US. Resistance rates for enrofloxacin, marbofloxacin, and chloramphenicol may be higher than reported in this analysis due to recent changes in MIC breakpoints in the Clinical and Laboratory Standards Institute VET01S (7th ed). The findings underscore significant geographical and temporal variations in resistance, emphasizing the need for tailored antimicrobial stewardship programs. CLINICAL RELEVANCE: The prevalence of MRS in companion animals poses treatment challenges and potential zoonotic risks. This study provides nationwide insight that was not previously available.

Authors: K. E. Sobkowich, A. Y. Hui, Z. Poljak, D. Szlosek, A. Plum and J. S. Weese Title: Nationwide analysis of methicillin-resistant staphylococci in cats and dogs: resistance patterns and geographic distribution Full source: Am J Vet Res, 2025,Vol 86, Iss 3, Author keywords 86
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OBJECTIVE: This study aims to quantify the frequency and resistance patterns of 3 methicillin-resistant staphylococci (MRS), Staphylococcus aureus (MRSA), Staphylococcus pseudintermedius (MRSP), and Staphylococcus schleiferi (MRSS), in companion animals, using historical culture and susceptibility data from a national diagnostic laboratory. METHODS: Samples from cats and dogs across the US, between 2019 and 2022, were analyzed. Methicillin-resistant isolates identified according to Clinical and Laboratory Standards Institute VET01S (5th ed) were included. Data included location, patient species, sampling site, year, and susceptibility results for various panels of antimicrobials. RESULTS: There were 110,423 MRSP, 5,618 MRSA, and 20,934 MRSS isolates identified. Methicillin-resistant S pseudintermedius was predominantly found in dogs (96.2%), with skin and soft tissue being the most common sites. Methicillin-resistant S aureus and MRSS were also primarily isolated from dogs, with significant yearly, regional, and species-specific differences in antimicrobial susceptibility observed. This study highlights high resistance levels in MRSP isolates, while MRSA and MRSS showed relatively higher susceptibility to several antimicrobials. CONCLUSIONS: This study provides insight into the distribution and antimicrobial resistance patterns of MRSA, MRSP, and MRSS in companion animals in the US. Resistance rates for enrofloxacin, marbofloxacin, and chloramphenicol may be higher than reported in this analysis due to recent changes in MIC breakpoints in the Clinical and Laboratory Standards Institute VET01S (7th ed). The findings underscore significant geographical and temporal variations in resistance, emphasizing the need for tailored antimicrobial stewardship programs. CLINICAL RELEVANCE: The prevalence of MRS in companion animals poses treatment challenges and potential zoonotic risks. This study provides nationwide insight that was not previously available.