Many yeasts and molds can cause opportunistic, even life-threatening infections in patients who are immunocompromised. These infections only rarely affect immunocompetent people. Yeasts tend to cause fungemia as well as focal involvement of skin and other sites.
(See also Overview of Fungal Infections.)
Blastoschizomyces capitatus and Trichosporon species (including T. ovoides, T. inkin, T. asahii, T. mucoides, T. asteroides, and T. cutaneum) are yeasts that cause often fatal disseminated infection, particularly in patients with neutropenia. Among Trichosporon, T. asahii is the most common cause of disseminated disease. The name T. beigelii, now obsolete, was formerly used for all or any of these Trichosporon species.
Malassezia furfur is a yeast that causes tinea versicolor and folliculitis and can also cause catheter-related sepsis in patients who are receiving parenteral lipids through a central venous catheter. Catheter-related sepsis typically affects infants and debilitated adults receiving lipid-containing IV hyperalimentation infusions. The microbiology laboratory personnel should be notified when attempting to isolate Malassezia from clinical specimens because special media are required.
Talaromyces marneffei (formerly called Penicillium marneffei) is an opportunistic pathogen causing disseminated infection in Southeast Asian patients with AIDS, and cases have been recognized in travelers returning to the United States after visiting that region. T. marneffei skin lesions may resemble molluscum contagiosum.
Especially in patients with neutropenia, various environmental molds, including species of Fusarium and Scedosporium apiospermum, both of which are becoming more frequent, can cause focal angioinvasive vasculitic lesions mimicking invasive aspergillosis. Fusarium species cause superficial infections (eg, keratitis, onychomycosis) in immunocompetent patients and disseminated infections in patients who are severely immunocompromised with prolonged, severe neutropenia and/or severe T-cell immunodeficiency. Fusarium species (unlike Aspergilli) may grow in routine blood cultures from patients with disseminated infection. Voriconazole is considered the medication of choice for both Fusarium and S. apiospermum.
Specific diagnosis requires culture and species identification and is crucial because not all of these organisms respond to a single antifungal. For example, Scedosporium species are typically resistant to amphotericin B. Optimal regimens of antifungal therapy for each member of this group of fungal opportunists must be defined.
