Rapid Identification of Malassezia furfur from other Malassezia Species: A Major Causative Agent of Pityriasis Versicolor

The present study is designed to evaluate the application of a simple method for rapid identification of Malassezia furfur among other Malassezia spp. based on production of a brownish-red pigment and its diffusion into the medium containing L-tryptophan as a sigle source of nitrogen. 91 strains of Malassezia (20% M. furfur, 2% M. sympodialis, 5% M. obtosa and 73% M. globosa) isolated from skin scales of 138 patients with pityriasis versicolor were examined. Reference Malassezia strains of all 7 species obtained from Centraalbureau voor Schimmelcultures, Baarn, the Netherlands, together with Candida albicans and Rhodotorula sp. were also studied. All of these strains were cultured on modified Dixon agar medium prepared by replacing pepton with equal amount (0.6%) of Ltryptophan. The pigment producing ability was evaluated after 7 days incubation of the cultures at 32 oC. Out of yeast species tested, all M. furfur strains produced specific brown pigment, whereas strains belonging to all other known Malassezia spp. and also several other yeasts failed to produce pigment. The results obtained further substantiated that study of pigment producing ability on this specific medium can be used as a simple and reliable test for rapid differentiation of M. furfur from other closely related Malassezia spp.. Iran J Med Sci 2004; 29(1):36-39.