Clinical characterization of Staphylococcus schleiferi infections and identification of risk factors for acquisition of oxacillin-resistant strains in dogs: 225 cases (2003-2009)

Abstract

Objective-To define clinical differences between coagulase-positive and coagulase-negative Staphylococcus schleiferi infections in dogs and to identify risk factors for the isolation of oxacillin-resistant S schleiferi. Design-Retrospective case series. Animals-225 dogs (yielding 225 S schleiferi isolates). Procedures-Information obtained from affected dogs' medical records included isolate body site source, antimicrobial treatments, and primary disease. For each dog, the S schleiferi isolate was characterized and antimicrobial susceptibility data were recorded. Risk factors for infection based on coagulase status and for S schleiferi oxacillin resistance were investigated. Results-Allergic dermatitis was the most common underlying disease (111/225 dogs). Ears (102 [45%]) and skin (95 [42%]) were sources of most of the 225 isolates. Isolate coagulase status was not significantly associated with any patient-level factors. Of the 225 isolates, 129 (57%) were oxacillin resistant. Coagulase-negative isolates were more likely to be oxacillin resistant than were coagulase-positive isolates (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.1 to 3.0). Administration of penicillin-based or first-generation cephalosporin drugs (OR, 3.0; 95% CI, 1.8 to 5.9) and third-generation cephalosporins (OR, 3.7; 95% CI, 1.1 to 12.3) within 30 days prior to culture were risk factors for oxacillin resistance. Conclusions and Clinical Relevance-Results suggested that coagulase-negative and coagulase-positive S schleiferi are potential pathogens in dogs and are often oxacillin resistant. Recent patient treatments with penicillin or cephalosporin were risk factors for oxacillin resistance. In clinical cases, full speciation of all Staphylococcus isolates should be performed and microbial treatments should be selected on the basis of results of susceptibility testing.