ZOOPATHOGENIC HETEROBASIDIOMYCETOUS YEASTS

Among the heterobasidiomycetous yeasts only a single species, Filobasi diella neoformans (anamorph Cryptococcus neoformans), is regularly enc ountered as a pathogen of humans and animals. A number of other yeasts with heterobasidiomycete affinities are known to be pathogens of huma ns and animals or are encountered in clinical specimens. These include Malassezia furfur, M. pachydermatis and M. sympodialis; Rhodotorula g lutinis, R. minuta, and R. rubra; Sporobolomyces spp.; and Trichosporo n beigelii (and the other Trichosporon spp. that have been suggested i n a recent revision of T. beigelii). In its most commonly encountered clinical form cryptococcosis is a disease of the central nervous syste m. The etiologic agent, C. neoformans, occurs in two varieties: C. neo formans var. neoformans and C. neoformans var, gattii, each with a sep arate ecological niche and geographic distribution. Humans are general ly quite resistant to overt disease and immunosuppression is often ass ociated with clinical disease. Malassezia furfur is a commensal of the skin and produces characteristic lesions of the skin and hair follicl es under poorly understood conditions. Invasive, systemic disease is r arely seen, but has been reported in immunocompromised individuals. Tr ichosporon beigelii is the cause of a well-known hair affliction, whit e piedra. Its exact location in nature, i.e., skin commensal or saprop hyte is unknown. Trichosporon spp. are customarily found as saprophyte s. T. beigelii may cause invasive systemic disease in immunocompromise d individuals. This species has recently been extensively revised, and a summary of that revision is presented. Rhodotorula rubra, the only species of Rhodotorula encountered in human infections, is a common co mmensal of the gastrointestinal tract. Invasive systemic disease cause d by R. rubra occurs rarely in immunocompromised patients. Sporobolomy ces spp. are encountered in clinical specimens, but pathogenicity has not been proven.