or moniliasis, infection caused by a yeastlike fungus belonging to the genus Candida, usually involving mucous membranes or the skin. Most cases are due to C. albicans or C. glabrata; other species that may cause disease include C. krusei, C. parapsilosis, and C. tropicalis. Candida fungi occur naturally in such parts of the body as the mouth, the gastrointestinal tract, and, in women, the vagina; they may also be acquired from external sources. The fungus is ordinarily kept in balance by bacteria present in the body, but if for some reason it multiplies abnormally, symptoms can result. Excessive multiplication may be triggered by such factors as a reduction in counterbalancing microorganisms because of antibiotic use, a change in hormone levels, or a weakening of the immune system as a result of illness (such as AIDS or diabetes), malnutrition, or certain medications (such as steroids or anticancer drugs).

Types.

Most oral fungal infections are due to Candida. Candidiasis of the mouth is commonly known as thrush. Sometimes, particularly in person who have AIDS or are receiving cancer chemotherapy, thrush may spread to the esophagus, causing esophagitis.Cutaneous, or skin, candidiasis—often showing up as moist, red patches, perhaps accompanied by small papules and pustules—is most likely to develop in moist underventilated skin areas. It may occur, for example, in the groin region and the crease of the buttocks, on the skin at the base of a fingernail, and in skin folds under large breasts. It may develop in the area covered by a diaper or on the hands of persons who use rubber gloves.

Vaginal candidiasis, often referred to simply as a vaginal yeast infection, is extremely common; it is estimated to affect three-quarters of all women at least once in their life. Symptoms generally include burning or itching sensations, sometimes accompanied by a thick vaginal discharge resembling cottage cheese; discomfort may be experienced during sexual intercourse. The infection is not commonly transmitted from person to person. In males who develop genital candidiasis an itchy rash may appear on the penis (balanitis).Various chronic Candida infections that involve the oral or vaginal mucous membranes, nails, or skin and tend to resist treatment are grouped together under the name “chronic mucocutaneous candidiasis.” They are often associated with a hormonal imbalance or an immune disorder or deficiency.

Rarely, candidiasis may take on an invasive form with Candida infecting the bloodstream (candidemia) and spreading throughout the body—for example, to the respiratory system (pulmonary candidiasis). Invasive candidiasis ordinarily occurs in persons with weakened natural resistance; the fungus typically enters the bloodstream through a catheter, ventilation tube, or surgical wound. Candidemia ranks as the fourth most common bloodstream infection among patients in U.S. hospitals. Candida may also enter the blood even of healthy individuals via a severe burn or trauma-caused wound or as a result of intravenous drug abuse. When left untreated, systemic candidiasis may produce a mortality rate approaching 50 percent.

Prevention and Treatment.

Recommendations commonly given for reducing the chances of developing candidiasis include keeping skin dry and clean, use of antibiotics only in accordance with a physician's instructions, and adherence to a healthy lifestyle and nutritious diet. People with diabetes are usually advised to maintain tight control over their blood sugar levels.

A variety of antifungal medications are available for treating candidiasis, among them the “polyenes” (nystatin and amphotericin B), which kill fungus cells, and the “azole” drugs (such as fluconazole, itraconazole, ketoconazole, and miconazole), which act mainly by inhibiting the growth of fungus cells. A recently introduced class of antifungal drugs known as the echinocandins has fungicidal action. It includes caspofungin, licensed by the U.S. Food and Drug Administration (FDA) in 2001 to treat difficult cases of invasive infection with the fungus Aspergillus and later approved by FDA for use also against esophageal candidiasis, candidemia, and certain types of invasive candidiasis; micafungin, approved in 2005 for treatment of esophageal candidiasis and for prevention of Candida infection in stem cell transplant patients; and anidulafungin, approved in 2006 for treating esophageal candidiasis, candidemia, and Candida-caused inflammation of the lining of the abdominal cavity.

See Fungus Infections.