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Chapter: Medical Microbiology: An Introduction to Infectious Diseases: Candida, Aspergillus, and Other Opportunistic Fungi

Candidiasis : Clinical Aspects

Superficial invasion of the mucous membranes by C. albicans produces a white, cheesy plaque that is loosely adherent to the mucosal surface.



Superficial invasion of the mucous membranes by C. albicans produces a white, cheesy plaque that is loosely adherent to the mucosal surface. The lesion is usually painless, un-less the plaque is torn away and the raw, weeping, invaded surface is exposed. Oral le-sions, called thrush, occur on the tongue, palate, and other mucosal surfaces as single or multiple, ragged white patches. A similar infection in the vagina, vaginal candidiasis, produces a thick, curd-like discharge and itching of the vulva. Although most women have at least one episode of vaginal candidiasis in a lifetime, a small proportion suffer chronic, recurrent infections. No general or specific immune defect has yet been linked to this syndrome.

C. albicans skin infections occur in crural folds and other areas in which wet, mac-erated skin surfaces are opposed. For example, one type of diaper rash is caused by C. albicans. Other infections of the skin folds and appendages occur in association withrecurrent immersion in water (eg, dishwashers). The initial lesions are erythematous papules or confluent areas associated with tenderness, erythema, and fissures of the skin. Infection usually remains confined to the chronically irritated area, but may spread beyond it, particularly in infants.

In rare persons with specific defects in T cell–mediated immune defense against Can-dida, a chronic, relapsing form of candidiasis known aschronic mucocutaneous candidi-asis develops. Infections of the skin, hair, and mucocutaneous junctions fail to resolve withadequate therapy and management. There is considerable disfigurement and discomfort, particularly when the disease is accompanied by a granulomatous inflammatory response. Although lesions may become extensive, they usually do not disseminate. To some degree this disease may represent a clinical example of immunologic tolerance. Cutaneous anergy to C. albicans antigens is commonly seen in these patients and is often reversed during antifungal chemotherapy, suggesting that it is due to chronic antigen excess.

Inflammatory patches similar to those in thrush may develop in the esophagus with or without associated oral candidiasis. Painful swallowing and substernal chest pain are the most common symptoms. Extensive ulcerations, deformity, and occasionally perforation of the esophagus may ensue. In immunocompromised patients, similar lesions may also de-velop in the stomach, together with deep ulcerative lesions of the small and large intestine.

Infection of the urinary tract via the hematogenous or ascending routes may produce cystitis, pyelonephritis, abscesses, or expanding fungus ball lesions in the renal pelvis. The clinical findings in disseminated infections of the kidneys, brain, and heart are gener-ally not sufficiently characteristic to suggest C. albicans over the bacterial pathogens, which more commonly produce infection of deep organs. Candidaendophthalmitis has the characteristic funduscopic appearance of a white cotton ball expanding on the retina or floating free in the vitreous humor. Endophthalmitis and infections of other eye struc-tures can lead to blindness.


Superficial C. albicans infections provide ready access to diagnostic material. Exudate or epithelial scrapings examined by potassium hydroxide (KOH) preparations or Gram smear demonstrate abundant budding yeast cells; if associated hyphae are present, the in-fection is almost certainly caused by C. albicansC. albicans is readily isolated from clinical specimens including blood if aerobic conditions are provided. Cultures from specimens such as sputum run the risk of contamination from the normal flora or a super-ficial mucous membrane lesion. A direct aspirate, biopsy, or bronchoalveolar lavage is of-ten required to establish the diagnosis.

Deep organ involvement is difficult to prove without a direct aspirate or biopsy. Even positive blood cultures must be interpreted with caution if they could represent colonization of intravenous catheters. Candida endocarditis represents a special diagnostic problem, because the yeasts seeding the blood from the valve may be filtered out in the capillary beds due to their large size. Arterial blood cultures may be required in this situation.

Although many serologic tests have been developed for detection of C. albicans anti-bodies, none of the methods developed to date has the sensitivity or specificity needed for clinical diagnosis. Immunologic techniques for detection of circulating Candida cell components such as mannan show promise, but none are yet practical for clinical use.


C. albicans is usually susceptible to amphotericin B, nystatin, flucytosine, and the azoles.Superficial infections are generally treated with topical nystatin or azole preparations. Measures to decrease moisture and chronic trauma are important adjuncts in treating Candida skin infections. Deeper C. albicans infections may resolve spontaneously withelimination or control of predisposing conditions. Removal of an infected catheter, con-trol of diabetes, or an increase in peripheral leukocyte counts is often associated with re-covery without antifungal therapy. Persistent relapsing or disseminated candidiasis is treated with amphotericin B, flucytosine, fluconazole, or combinations of amphotericin B with other drugs. Fluconazole has been the most effective treatment for chronic mucocu-taneous candidiasis.

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Medical Microbiology: An Introduction to Infectious Diseases: Candida, Aspergillus, and Other Opportunistic Fungi : Candidiasis : Clinical Aspects |

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