Yeasts

The number of yeast species documented to cause invasive infections in humans has increased. Several uncommon Candida species have now been described to cause invasive infection in humans. A case of cryptococcosis due to the Vancouver Island strain of Cryptococcus gattii acquired in Washington State was also recently reported. Other Cryptococcus species are also increasingly being recognized as causes of invasive disease among immunocompromised hosts. A list of ascomycetous yeasts such as Clavispora , Debaryomyces and Dipodascus reported to cause human disease have been discussed in the chapter. Compared to ascomycetes, yeasts of the phylum Basidiomycota are generally less frequently implicated in human disease. Malassezia and Trichosporon are some of the basidiomycetous yeasts that have been discussed in the chapter. Culture methods remain the most frequently utilized laboratory tools for the diagnosis of invasive yeast infections. Various diagnostic approaches including chromogenic media, rapid biochemical assays, commercial biochemical panels, in vitro susceptibility testing, and molecular identification techniques are analyzed in the chapter.