Candida albicans is responsible for most yeast infections in humans. In addition to causing ordinary vaginal and oral (thrush) infections, this fungus is a serious threat to immunocompromised patients, for whom disseminated, invasive candidiasis is common and often fatal (31, 56).The fungus is normally maintained as a harmless commensal on skin, on mucosa, and in the gut (23) but becomes an opportunistic pathogen upon entry into the bloodstream of immunocompromised (particularly neutropenic) individuals