Background - Canine pyodermas associated with meticillin-resistant Staphylococcus spp. (MRS) have increased in prevalence over the past decade. Hypothesis/Objectives - To compare the prevalence of MRS isolation from dogs with superficial pyoderma at a primary care clinic (PCC) and those at a tertiary care facility (VMTH) in California, USA, and identify associated risk factors. Animals - Client-owned dogs from the VMTH (80 dogs) and the PCC (30 dogs). Methods - Aerobic bacterial culture and antibiotic susceptibility were performed on swab specimens collected from dogs, and meticillin resistance was determined using microdilution methods according to Clinical and Laboratory Standards Institute guidelines. A mecA gene PCR assay was used to confirm meticillin resistance when possible. Results - Of 89 staphylococcal isolates from the VMTH, 34 (38.2%) were meticillin resistant. In 31 dogs, pyoderma persisted, and one or more follow-up isolates were obtained. The species isolated and drug susceptibility changed unpredictably during treatment. Of 33 PCC isolates, nine (27.3%) were meticillin resistant. Multiple drug resistance was identified in 41 of 53 (77.3%) MRS isolates from the VMTH and five of nine from the PCC. The sensitivity and specificity of PCR for the detection of meticillin resistance was 34 of 39 (87%) and 86 of 87 (99%), respectively. Risk factors for meticillin resistance for both sites were antibiotic treatment within the last year (P=0.001), and for VMTH, hospitalization of dogs within the last year (P=0.001). Conclusions and clinical importance - The prevalence of meticillin resistance was not different between VMTH and PCC isolates (P=0.29). Previous antimicrobial therapy was an important risk factor for the isolation of MRS at both sites.
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