Candida (fungus)

Candida albicans PHIL 3192 lores

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Candida spores and pseudohyphae

Candida is a genus of yeasts and is the most common cause of fungal infections worldwide. Many species are harmless commensals or endosymbionts of hosts including humans; however, when mucosal barriers are disrupted or the immune system is compromised they can invade and cause disease, known as an opportunistic infection. Candida albicans is the most well-known and significant species that can cause various infections, collectively referred to as candidiasis.

Characteristics

Candida species are small, oval yeasts that reproduce by budding. Under certain conditions, some species can develop pseudohyphae, or false hyphae, which are elongated yeast cells that resemble filaments. This morphological change is associated with the pathogenic phase of the yeast. The ability to switch between yeast forms and pseudohyphae is linked to virulence in Candida species, particularly in Candida albicans.

Habitat and Ecology

Candida species are commonly found in the human body as part of the normal flora of the skin, mouth, intestines, and vagina, where they usually cause no harm. They can also be found in the environment, such as in soil, on fruits, and other organic matter. The balance of microorganisms in the body is a delicate one, and when it is disturbed, Candida can multiply and lead to infection.

Pathogenesis

Candida species can cause infections ranging from superficial, such as oral thrush and vaginal yeast infections, to systemic and potentially life-threatening diseases like candidemia and invasive candidiasis. The transition from commensal to pathogen can be triggered by various factors, including antibiotic use, which reduces bacterial competition, changes in the host's immune system, and physical disruptions to mucosal barriers.

Diagnosis and Treatment

Diagnosis of Candida infections involves both clinical assessment and laboratory tests, including culture and microscopy of samples, and, more recently, molecular methods. Treatment depends on the severity and location of the infection. Superficial infections are typically treated with topical antifungal agents, while more severe systemic infections require oral or intravenous antifungals, such as fluconazole or amphotericin B.

Prevention

Prevention of Candida infections involves maintaining a healthy microbiota through a balanced diet, avoiding unnecessary antibiotics, and practicing good hygiene. For individuals with weakened immune systems, prophylactic antifungal medications may be prescribed to prevent infection.