In vitro susceptibility of Pityrosporum ovale (Malassezia furfur) to human androgenic steroids.

Cells of Pityrosporum ovale that colonize human pilosebaceous units are constantly exposed to cutaneous androgenic steroids. The aim of our study was to find out whether P. ovale is susceptible to these hormones. Three strains of P. ovale were grown in vitro in the presence of various concentrations of testosterone, dehydroepiandrosterone, androstenedione, androstanedione, 5-alpha-dihydrotestosterone and progesterone (10, 100, and 1000 micrograms/ml; agar dilution assays). In addition, three strains of Candida albicans were also exposed to equal concentrations of the same androgens. As a result, all P. ovale strains were suppressed by 1000 micrograms/ml androstenedione, which was the strongest inhibitor. The other androgenic steroids also significantly reduced P. ovale growth at different concentrations, depending on the hormone used and the strain tested. Progesterone was inhibitory at the highest concentration for one P. ovale strain only. Candida albicans was not affected by any of the androgens. These findings demonstrate an in vitro susceptibility of P. ovale to high concentrations of human androgenic steroids. A relevance of this interaction for the in vivo fungus-host relation is not apparent.