Factors associated with methicillin-resistant versus methicillin-susceptible Staphylococcus pseudintermedius infection in dogs.

Objective: To compare methicillin-resistant Staphylococcus pseudintermedius (MRSP) and methicillin-susceptible S pseudintermedius (MSSP) infections in dogs.

Design: Multicenter case-control study.

Animals: Dogs with MRSP infections were matched, by hospital, with 2 MSSP controls, with the infections occurring immediately before and after the case infection.

Procedures: Signalment, historical, clinical, treatment, and outcome data were documented. Conditional logistic regression was performed. A manual stepwise backward elimination procedure was used to build the multivariable model.

Results: 56 case and 112 control dogs were enrolled. Pyoderma was the most common infection type in both groups. In the final multivariable model, systemic administration of antimicrobials within 30 days prior to infection was significantly associated with an MRSP versus an MSSP infection (OR, 9.9; 95% confidence interval, 3.59 to 27.53).

Conclusions And Clinical Relevance: The association of prior antimicrobial administration and MRSP infection indicated the potential impact of routine antimicrobial use in veterinary medicine on antimicrobial resistance and the need for prudent use of these important drugs. Mortality rate was not significantly different between MRSP and MSSP infections; the lack of a significant difference suggested that MRSP was inherently no more virulent than MSSP, provided the infection was properly diagnosed and appropriate treatment was started. Basic concepts such as prudent antimicrobial use and early diagnosis through timely submission of appropriate culture specimens therefore can be important measures to try to reduce the impact of this pathogen.