Dimorphism of Pityrosporum orbiculare in a defined culture medium.

Dimorphism of Pityrosporum orbiculare was induced in an artificial culture medium which consisted of 0.05 M glycine in 0.03-0.06 M ammonium phosphate buffer (pH 5.6), salts, glucose, and Tween-80. Of the strains tested, 78 to 85% produced hyphal elements from up to 8.5% of yeast cells. Morphologic features of P. orbiculare in culture were examined by scanning electron microscopy and compared with the appearance of fungus from clinical lesions of tinea versicolor. Morphologically, the fungi obtained in vivo and in vitro were identical.