thrush, in medicine, infection caused by the fungus Candida albicans, manifested by white, slightly raised patches on the mucous membrane of the tongue, mouth, and throat. The mucous membrane beneath the patches is usually raw and bleeding. The overgrowth of this fungus results when the balance in the normal oral microbe population is disturbed by antibiotic therapy or disease. It occurs most frequently in infants, in adults suffering from chronic illnesses, in the debilitated, in the immunosuppressed, and in individuals on long-term antibiotic, corticosteroid, or antineoplastic therapy. It is often an early symptom of AIDS. Treatment is with antifungal drugs, such as nystatin.