Taxonomy of the Genus Malassezia

Ahn, Kyu Joong

Abstract

The yeasts of the genus Malassezia, of which type species is Malassezia furfur(Robin) Baillon 1889, are dimorphic and lipophilic and are members of the normal cutaneous flora in humans. Early taxonomic descriptions of Malassezia yeasts were limited by the failure of investigators to culture this fungus and were based solely on micromorphological descriptions of the organism in skin samples. The culture could be possible only after the lipophilic nature of this fungus was demonstrated and the question of dimorphism was solved. Malassezia has been the genus name formally accepted for both phases of growth, mycelia(Malassezia) and yeasts(Malassezia). Variations in the morphology of Malassezia species were noted even some of the earliest descriptions of the organism in the skin. Stable morphological, physiological and immunological variants have been claimed and the taxonomic status of these has been becoming realized with the application of molecular techniques. Recently, the genus Malassezia was revised using morphology, ultrastructure, physiology and molecular biology by Gu ho et al.. As a result the genus has been enlarged to include seven species comprising M. furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtusa M. restricta and M. slooffiae. Malassezia yeasts reside predominantly in regions of high sebum excretion as members of the microbiological flora of the skin. Malassezia yeasts are also implicated in various diseases, including pityriasis versicolor, Malassezia folliculitis, seborrheic dermatitis and systemic fungal infections.