Candida albicans is a dimorphic yeast that normally lives as a harmless commensal in the human mouth, gut and genital tract. It is opportunistic, meaning it can cause disease when host defenses are compromised or the microbial balance is disturbed.
Explanation
C. albicans belongs to the Ascomycota division and exhibits remarkable morphological plasticity, switching between unicellular budding yeast, elongated pseudohyphae and true hyphal filaments in response to environmental cues. This ability aids colonization and invasion; hyphae can penetrate epithelial layers and form biofilms on mucosal surfaces and medical devices. Under normal conditions, the organism is kept in check by the immune system and by competing microbiota. Factors such as broad‑spectrum antibiotics, high estrogen levels, diabetes, immunosuppression and HIV infection disrupt this balance, allowing C. albicans to proliferate and cause candidiasis. Superficial infections include oral thrush, vaginal yeast infections and diaper rash. The fungus can also cause urinary tract infections and chronic mucocutaneous candidiasis. In immunocompromised patients, C. albicans may enter the bloodstream, leading to systemic candidemia with high mortality. Diagnosis involves microscopy of budding yeast with pseudohyphae, culture on selective media like CHROMagar Candida, and the germ tube test, in which serum incubation induces short hyphal outgrowths characteristic of C. albicans. Treatment depends on severity: topical azoles for mucosal infections, and systemic antifungals such as fluconazole or echinocandins for invasive disease.
Clinical Significance and Examples
Oral thrush presents as white plaques on the tongue and cheeks, often in infants or denture wearers. Vulvovaginal candidiasis causes itching and thick discharge; recurrence may be triggered by antibiotic therapy or hormonal changes. C. albicans can colonize central venous catheters and prosthetic heart valves, forming biofilms that are resistant to antifungal drugs. Systemic infections occur predominantly in patients with neutropenia, organ transplants or intensive care stays. Research on C. albicans continues to illuminate its genetics, host interactions and mechanisms of pathogenicity.
By understanding this common yeast and the conditions that allow it to become pathogenic, clinicians can better prevent and manage candidiasis in vulnerable populations.
Related Terms: yeast, dimorphic, candidiasis, commensal, opportunistic pathogen