Normal fungal flora of the skin

As with bacteria, the fungal flora on the surface of the stratum corneum of otherwise healthy persons can be regarded as consisting of two types of populations – transient and resident commensals. The resident members are the Pityrosporum (Malassezia) or lipophilic yeasts, which are found on the skin surface of all adults and cluster around the openings of sebaceous glands. The existence of a transient fungal skin flora has not been as well documented as that of the bacteria, although temporary colonization of nails and hair by dermatophytes, and of other sites by Candida spp. is recognized. Transient colonization may also reflect contamination from another site where carriage rates are comparatively higher. For example, the isolation of yeasts from the perineum may well reflect their presence in the gastrointestinal tract and, in women, in the vagina.

Malassezia (Pityrosporum) yeasts

Members of the genus Pityrosporum are thick-walled yeast fungi that inhabit the superficial layers of the stratum corneum. They comprise three main species or varieties – Pityrosporum ovale, P. orbiculare and P. pachydermatis. The first two of these are found chiefly on human hosts and P. pachydermatis on a variety of other hosts. Pityrosporum ovale and P. orbiculare are associated with certain human diseases including pityriasis versicolor, where yeasts and short, stubby hyphae can be demonstrated in skin scrapings. These hyphae were originally named, without cultural confirmation, Malassezia furfur, but are now known to represent a parastic phase of pityrosporum.