Treatment of Meticillin-Resistant Staphylococcus Pyoderma With Rifampicin in 104 Dogs: Clinical Outcomes, Adverse Effects, and Rifampicin Resistance in Nonresponders.

Abstract

BACKGROUND: Meticillin-resistant Staphylococcus pseudintermedius (MRSP) is often resistant to multiple antibiotics. Rifampicin is effective against most MRSP isolates, yet the potential for the development of rapid resistance raises questions regarding its suitability as an antibiotic monotherapy for MRSP pyoderma. OBJECTIVES: To describe the: (i) clinical outcome of rifampicin antibiotic monotherapy in MRSP pyoderma; (ii) frequency of adverse effects; and (iii) development of rifampicin resistance among dogs considered nonresponders to therapy. MATERIALS AND METHODS: A retrospective study of medical records from 1/1/2013 to 1/12/2022 of client-owned dogs with MRSP pyoderma treated with oral rifampicin as a systemic antibiotic monotherapy for 21 days. RESULTS: 104 dogs were included; 77 cases of superficial pyoderma (74%) and 27 cases of deep pyoderma (26%). The mean daily rifampicin dose was 6 mg/kg. Rifampicin was clinically effective in 86 cases (82.7%). Eleven of 18 nonresponding dogs demonstrated rapidly acquired rifampicin resistance (10.6%). Eighty-two (78.8%), 17 (16.3%), two (1.9%) and three (2.9%) dogs experienced zero, mild, moderate and severe adverse effects, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Rifampicin at 6 mg/kg is an effective and mostly well-tolerated monotherapy for treating MRSP pyoderma. However, in this study, it was associated with rapid development of resistance in ≥ 10% of treated dogs. Inadequate clinical response occurred without demonstrable resistance in 6.7% of cases. Concurrent use of ciclosporin or fluconazole with rifampicin increased the odds of severe adverse reactions.