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Fungal infections, or mycoses, may be broken into two broad categories: (a) endemic and (b) opportunistic. The endemic mycoses are those in which susceptibility to the infection is acquired by living in a geographic area constituting the natural habitat of the particular fungus. The most commonly encountered endemic mycoses in North America are due to Histoplasma capsulatum, Coccidioides immitis/posadasii, Blastomyces dermatitidis, and Sporothrix schenckii. Infection due to these agents is usually acquired by inhalation of conidia from an environmental source. Although infections with these fungal pathogens are clearly important, a more pressing problem now is that of the opportunistic mycoses, which carry a particularly high mortality and appear to be increasing significantly.
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The opportunistic mycoses occur primarily in immunocompromised patients, particularly those with malignancies and acquired immunodeficiency syndrome (AIDS) and after major surgery, severe burn injury, blood and marrow (BMT) and solid organ (SOT) transplantation. Contributing factors include exposure to broad-spectrum antibacterial agents, adrenal corticosteroids, and cytotoxic chemotherapeutic agents and prolonged use of indwelling catheters. The most important agents of the opportunistic mycoses are Candida spp., Cryptococcus neoformans, Aspergillus spp., and the Zygomycetes.
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The prevention, diagnosis, and therapy of opportunistic mycoses remain extremely difficult. Increased recognition of the importance of these infections has spurred efforts to develop new diagnostic and therapeutic approaches, as well as expand our knowledge of the epidemiology and pathogenesis of the mycoses.
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Clinical and Epidemiologic Features
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Candida species are commonly found as part of the endogenous microbial flora of the oropharynx, gastrointestinal tract, and vagina of a variable proportion of normal persons. Although Candida albicans remains the most common cause of local and disseminated infection, there has been an increase in infections caused by Candida tropicalis, Candida parapsilosis, Candida krusei, Candida glabrata, and Candida lusitaniae among others.1,2,3,4,5,6,7,8
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The clinical manifestations of candidiasis include local mucocutaneous infection and hematogenously disseminated candidiasis. Local mucocutaneous candidiasis is most commonly caused by C. albicans and may involve the oropharynx (thrush) and the entire gastrointestinal tract, including the esophagus, stomach, and large and small bowel. Genitourinary tract involvement includes cystitis and vulvovaginal candidiasis. Superficial infections of the skin are less common but may involve the axillae, groin, inframammary folds, perianal region, and other warm moist areas, particularly following antimicrobial therapy. Although vulvovaginitis commonly occurs in otherwise normal, healthy women, mucocutaneous candidiasis most commonly occurs in immunocompromised patients: neonates, the elderly, patients with AIDS, and patients hospitalized with various malignancies and following organ transplantation and major surgery. Prolonged exposure to multiple broad-spectrum antibiotics may promote mucosal overgrowth of Candida spp. and thus predispose these patients to superficial candidiasis.1,9
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Chronic mucocutaneous candidiasis is a rare syndrome associated with defects in T cell-mediated immunity. These patients have persistent ...