Many yeasts and molds can cause opportunistic, even life-threatening infections in immunocompromised patients. 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 Overview of Fungal Infections Fungal infections are often classified as either Opportunistic Primary Opportunistic infections are those that develop mainly in immunocompromised hosts. Primary infections can develop in immunocompetent... read more .)
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 neutropenic patients. 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 Tinea Versicolor Tinea versicolor is skin infection with Malassezia furfur that manifests as multiple asymptomatic scaly patches varying in color from white to tan to brown to pink. Diagnosis is based on clinical... read more and folliculitis Folliculitis Folliculitis is an infection of hair follicles. Diagnosis is clinical. Treatment is with topical clindamycin. (See also Overview of Bacterial Skin Infections.) The etiology of folliculitis is... read more 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 invader causing disseminated infection in Southeast Asian patients with AIDS, and cases have been recognized in travelers returning to the US after visiting that region. T. marneffei skin lesions may resemble molluscum contagiosum.
Especially in neutropenic patients, 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 Aspergillosis Aspergillosis is an opportunistic infection that usually affects the lower respiratory tract and is caused by inhaling spores of the filamentous fungus Aspergillus, commonly present in the environment... read more . Fusarium species cause superficial infections (eg, keratitis, onychomycosis Onychomycosis Onychomycosis is fungal infection of the nail plate, nail bed, or both. The nails typically are deformed and discolored white or yellow. Diagnosis is by appearance, wet mount, culture, polymerase... read more ) in immunocompetent patients and disseminated infections in severely immunocompromised patients 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 drug 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 any single antifungal drug. 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.