The in vitro effect of fluconazole on the filamentous form of Pityrosporum ovale.

The antimycotic activity of fluconazole against the filamentous form of Pityrosporum ovale was studied in vitro. P. ovale was grown on human stratum corneum in vitro with and without the addition of different concentrations of fluconazole. In control cultures hyphae were produced in 25% of the cells compared to only 4% after exposure to fluconazole 1 microgram/ml. In control cultures 16% of the fungal cells showed signs of necrosis, due to the normal turnover rate of the cells, compared to 65% of the fungal cells exposed to 1 microgram/ml of fluconazole. In the transmission electron microscope the typical thick-walled fungal cells with their characteristic budding were observed in control cultures. However, after exposure to 1 microgram/ml of fluconazole that P. ovale cells showed extensive signs of necrosis, with loss of internal organelles and disinterruption of the cell wall. The results obtained in this in vitro model mimic the in vivo situation in pityriasis versicolor. There is a parallel between the good results obtained in this system and the good clinical effect of fluconazole in Pityrosporum-related diseases.