An in vivo procedure to evaluate antifungals agents on Malassezia pachydermatis in dogs: example with a piroctone olamine containing shampoo

Abstract Objective. – The first objective of the present study was to develop an in vivo procedure as a possible model to evaluate the activity of topical antifungal agents against Malassezia pachydermatis . The second objective was to apply this procedure to assess the antifungal properties of a shampoo containing piroctone olamine. Materials and methods. – Twenty beagle dogs, maintained in laboratory conditions, were divided in two equivalent groups (treated and untreated) based on initial counts of spontaneous Malassezia pachydermatis populations on skin and ear canals. The treated group received one application of a shampoo containing piroctone olamine on the ventral neck and ear canals were filled with diluted shampoo. Samples for fungal cultures were taken from skin and ear canals on days 0 (before treatment), 1–2 and 4 and then cultured on modified Sabouraud's agar. On day 7 the number of colony forming units of Malassezia pachydermatis (CFU) on cultures was counted. Results. – The present study demonstrated: (i) the value of an original procedure for evaluating in a group of laboratory dogs the in vivo activity of anti- Malassezia topical products under controlled experimental conditions; (ii) the CFU counts at the three sites progressively decreased in the treated group from D 0 to D 4 while they remained constant in the non-treated group. Analysis of variance showed a significant interaction effect between treatment and time at the left ear site ( P Conclusion. – The three sites chosen, ear canals and ventral neck, in groups of healthy dogs, can be used to evaluate the evolution of resident populations of Malassezia pachydermatis . The results of this study indicated also an unexpected prolonged antifungal effect obtained with a shampoo containing piroctone olamine that could be of interest when Malassezia overgrowth is observed in dogs.