Immediate and residual antifungal activity of compounds used for whole body and adjuvant topical therapy against Microsporum canis: an in vitro study.

Abstract

Topical antifungal therapy is recommended to disinfect hairs of dermatophyte-infected animals. To determine the immediate and residual (24, 48 and 72h) antifungal activity of commonly used products for focal (n=11) and whole body application (n=3). Hair samples from naturally infected kittens. Immediate antifungal activity was assessed using isolated infected spores. In a more robust challenge, toothbrushes containing whole infected hairs were repeatedly treated with products until culture-negative. Residual activity was determined by treating 0.04g of uninfected hair with test products, allowing hairs to dry and then plating hairs onto fungal culture plates inoculated with Microsporum canis. Residual activity was assessed at 24, 48 and 72h post-treatment. All products showed good efficacy against isolated infected spores. Two products required three treatments to disinfect whole infected hairs (miconazole 0.2% and ketoconazole 0.15%); all other products were efficacious after one treatment. For each product residual activity at 24, 48 and 72h was similar. For the whole body products, lime sulfur and enilconazole showed residual activity, but as expected none was detected for 2% miconazole nitrate/ 2% chlorhexidine shampoo. For focal therapy products, residual activity was detected for clotrimazole 1%, terbinafine 1%, miconazole at 0.2, 1 or 2%(with or without chlorhexidine), climbazole 0.5% with chlorhexidine gluconate, and ketoconazole 1% with chlorhexidine gluconate. A ketoconazole 0.15% with 0.15% chlorhexidine gluconate showed no residual activity. Findings support twice weekly application of enilconazole and lime sulfur, and application of adjuvant focal topical therapy daily or every other day.