Growth and filament production of Pityrosporum orbiculare and P. ovale on human stratum corneum in vitro.

When Pityrosporum orbiculare and P. ovale were incubated with stratum corneum epithelial cells, suspended in phosphate-buffered saline for 90 min at 37 degrees C, short filaments were produced in 11-17.5% of the yeast cells. A successful culture of P. orbiculare and P. ovale on human stratum corneum in vitro is described. When the stratum corneum pieces were incubated for 5 days in an environment with 7% CO2, a picture resembling that seen microscopically in tinea versicolor was observed. Filaments were produced in 39-48% of P. orbiculare and P. ovale cells; the longest pseudohyphae, 40-60 microns, were produced by P. ovale. This culture method provides the possibility of studying the parasitic mycelium form of P. orbiculare and P. ovale in vitro. The influence of antimycotics, other drugs, and interaction with other microorganisms can be studied.