Tinea versicolor and Pityrosporum orbiculare: a mycological investigation.

It has generally been accepted that the cause of tinea versicolor is the dimorphic lipophilic fungus Pityrosporum orbiculare. In this investigation the fungus was cultured from all patients with tinea versicolor. It was also isolated from normal-looking skin and apparently healed lesions in a high proportion of patients with tinea versicolor; from patients with seborrheic dermatitis, and from healthy volunteers.Isolation of P. orbiculare was most satisfactorily achieved on a peptone-glucose-yeast extract medium containing glycerol monostearate, overlaid with olive oil. Germ tubes were produced when P. orbiculare was incubated in an atmosphere containing air with 7% CO2. Cultures of P. orbiculare and P. ovale did not show fluorescence in Wood's light.