Cryptococcus neoformans is an encapsulated yeast belonging to the class Tremellomycetes and an obligate aerobe that can live in both plants and animals. Its teleomorph is a filamentous fungus, formerly referred to Filobasidiella neoformans. In its yeast state, it is often found in bird excrement. Cryptococcus neoformans can cause disease in apparently immunocompetent, as well as immunocompromised, hosts
Cryptococcus neoformans has undergone numerous nomenclature revisions since its first description in 1895. It formerly contained two varieties: C. neoformans var. neoformans and C. neoformans var. grubii. A third variety, C. neoformans var. gattii, was later defined as a distinct species, Cryptococcus gattii. The most recent classification system divides these varieties into seven species. C. neoformans refers to C. neoformans var. grubii. A new species name, Cryptococcus deneoformans, is used for the former C. neoformans var. neoformans. C. gattii is divided into five species.
The teleomorph was first described in 1975 by K.J. Kwon-Chung, who obtained cultures of Filobasidiella neoformans by crossing strains of the yeast C. neoformans. She was able to observe basidia similar to those of the genus Filobasidium, hence the name Filobasidiella for the new genus.Following changes to the International Code of Nomenclature for algae, fungi, and plants, the practice of giving different names to teleomorph and anamorph forms of the same fungus was discontinued, meaning that Filobasidiella neoformans became a synonym of the earlier name Cryptococcus neoformans.
