Candida albicans: pathogenesis and spectrum of disease
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p773
2025-12-07
67
Candidiasis is an infection caused by a Candida spp. It may include oroesophageal candidiasis, intertriginous candidiasis (in which skin folds are involved), paronychia, onychomycosis, perlèche respiratory infections, vulvovaginitis, thrush, pulmonary infection, eye infection, endocarditis, meningitis, fungemia or candidemia, or disseminated infection. Paronychia is an infection of the tissues surrounding the nails, and onychomycosis is an infection of the nail and nail bed. Thrush, an infection of the mucous membranes in the mouth, is considered a localized infection. Thrush can be seen in newborns, patients with human immunodeficiency virus (HIV) infection, individuals with diabetes, and patients undergoing chemotherapy. Creamy patches or colonies appear on the tongue and mucous membranes. Candida organisms may be recovered from the oropharynx, gastrointestinal (GI) tract, genitourinary tract, and skin.
The clinical significance of candidal organisms recovered from respiratory tract secretions is difficult to deter mine, because Candida spp. are considered part of the normal oropharyngeal flora of humans. A study at the Mayo Clinic evaluated the clinical significance of yeasts other than C. neoformans that are recovered from respiratory secretions. These researchers concluded that such yeasts are part of the normal flora and do not need to be routinely identified. Similarly, Barenfanger et al. demonstrated that routine identification of yeasts from respiratory specimens results in unnecessary antifungal therapy, an extended hospital stay, and increased health care costs without demonstrable benefit. Simultaneous recovery of the same species of yeast from several body sites, including urine, is a good indicator of disseminated infection and fungemia.
The pathogenesis of candidal infections is extremely complex and probably varies with each species. Adhesion of Candida organisms to the epithelium of the gastrointestinal or urinary tract is a crucial factor. Candida spp. commonly colonize mucosal surfaces. Their ability to invade and cause infection depends on adherence to the surface before infection. Three distinct aspartyl proteases have been described in C. albicans, and strains with high levels of proteases have been shown to have an increased ability to cause disease in experimental animal models. Hydrophobic molecules on the surface of Candida spp. also appear to be important in pathogenesis, and a strong correlation exists between adhesion and surface hydrophobicity. In addition, high levels of phospholipase, found in strains of C. albicans, have correlated with a higher mortality rate in experimental animals compared with experimental infections caused by strains that produce a lower level of phospholipase. Phenotypic switching (i.e., the ability to produce pseudohyphae and hyphae), seen in C. albicans, also may play a role in pathogenesis.
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