Fluorometric assessment of in vitro antidermatophytic activities of antimycotics based on their keratin-penetrating power

Keratin particles impregnated with amorolfine or clotrimazole in serial dou bling dilutions (64 to 0.125 mu g/ml) were used to evaluate the activities of these agents against 20 isolates each of Trichophyton mentagrophytes and Trichophyton rubrum in a yeast carbon broth medium incorporating Alamar Bl ue dye. The proposed MIC with keratin impregnation (MICK) is defined as the lowest concentration of an agent used to impregnate keratin particles that effects a fluorescence-based fungal growth quotient of 0.05 or less, The c onventional colorimetric and visual MICs of amorolfine for the dermatophyte s, less than or equal to 0.03 mu g/ml for T. mentagrophytes and less than o r equal to 0.063 mu g/ml for T. rubrum, were approximately half of those of clotrimazole for the same isolates. The superiority of the MIC(K)s of amor olfine for isolates of T. mentagrophytes (2.0 mu g/ml; range, 0.5 to 8.0 mu g/ml) and T. rubrum (4.0 mu g/ml; range, 2.0 to 8.0 mu g/ml) over those of clotrimazole (32 mu g/ml [range, 8.0 to >64 mu g/ml] and 64 mu g/ml [range , 16 to >64 mu g], respectively) may indicate the strong in vivo antidermat ophytic activity of amorolfine as a topical agent. The new antidermatophyti c susceptibility testing procedure has potential clinical utility for the i n vitro screening of agents for use in the topical treatment of superficial mycoses.