In vitro efficacy of 0.2% and 0.4% sodium oxychlorosene against meticillin‐resistant Staphylococcus pseudintermedius

Background There is a need for alternative topical therapies as a consequence of the increased prevalence of meticillin‐resistant Staphylococcus pseudintermedius (MRSP) skin infections in dogs. Sodium oxychlorosene has been used as a topical antibacterial agent in human medicine since 1955. Objectives To determine whether 0.2% and 0.4% sodium oxychlorosene solutions have a bactericidal effect (>3‐log reduction) on MRSP strains isolated from canine skin infections. Methods and materials A genetically heterogeneous collection of MRSP isolates from dogs was assembled from laboratories across the United States. Time–kill assays were performed with 0.2% and 0.4% sodium oxychlorosene on a 0.5 McFarland standard [approximately 108 colony‐forming units (cfu/ml)] suspension of each strain. The average bacterial counts (cfu/ml) of each MRSP strain then were determined at 5, 10, 20 and 60 s after exposure to sodium oxychlorosene; cfu/ml data were converted to log10 scale to calculate microbial reduction. Results The average bacterial counts following exposure to the 0.2% solution at 5, 10, 20 and 60 s were 6.94 × 104, 5.63 × 103, 2.96 × 102 and 1.48 × 102 cfu/ml, respectively. For the 0.4% solution, the average bacterial count at 5 s was 2.12 × 103 cfu/ml. No bacterial growth was observed for any MRSP strain by 10 s. The greatest reduction in cfu/ml occurred within 5 s following exposure to each solution 3.4‐log and 4.9‐log reduction for 0.2% and 0.4%, respectively. Conclusions and Clinical Relevance 0.2% and 0.4% sodium oxychlorosene solutions have a bactericidal effect (>99.9% reduction) against MRSP in vitro. Further in vivo studies are necessary to determine whether it is an appropriate alternative therapy for canine pyoderma Résumé Contexte Il existe un besoin de thérapies topiques alternatives en raison de la prévalence accrue d'infections cutanées à Staphylococcus pseudintermedius résistante à la méticilline (MRSP) chez les chiens. L'oxychlorosène de sodium est utilisé comme agent antibactérien topique en médecine humaine depuis 1955. Objectifs Déterminer si les solutions d'oxychlorosène de sodium à 0,2 % et 0,4 % ont un effet bactéricide (réduction > 3 log) sur les souches de MRSP isolées d'infections cutanées canines. Méthodes et matériaux Une collection génétiquement hétérogène d'isolats de MRSP provenant de chiens a été constituée à partir de laboratoires à travers les États‐Unis. Des essais de destruction du temps ont été effectués avec 0,2 % et 0,4 % d'o