Candidiasis

Candidiasis is infection caused by yeasts of the genus Candida, most often Candida albicans. It spans a wide clinical range — from superficial infection of mucous membranes and skin, such as oral and vulvovaginal thrush, to invasive bloodstream and deep-organ disease in vulnerable hosts.

Definition

Candidiasis is infection by Candida yeasts, ranging from superficial mucocutaneous disease (e.g., oral, oesophageal, vulvovaginal, cutaneous) to invasive candidiasis, in which the organism reaches the bloodstream (candidaemia) or deep tissues.

Scope

This topic covers Candida as a commensal that can turn pathogenic, the spectrum from mucocutaneous to invasive candidiasis, the host and iatrogenic factors that shift the balance toward disease, the epidemiology of candidaemia, and the growing concern of antifungal resistance. It is reference material and does not give dosing or individualised treatment advice.

Key concepts

• Candida as commensal and opportunist
• Candida albicans and non-albicans species
• Mucocutaneous candidiasis (oral, oesophageal, vulvovaginal, cutaneous)
• Invasive candidiasis and candidaemia
• Risk factors: catheters, broad-spectrum antibiotics, neutropenia, ICU stay
• Species shift and antifungal resistance
• Candida auris as an emerging multidrug-resistant species

Mechanisms

Candida species are common commensals of the gastrointestinal tract, skin, and mucosae. Disease develops when local or systemic conditions favour overgrowth and tissue invasion — disruption of the microbiome by broad-spectrum antibiotics, impaired mucosal or immune defences, or breaches of barriers such as central venous catheters. Superficial disease reflects mucosal or cutaneous overgrowth, while invasive candidiasis follows translocation from the gut or entry along vascular devices into the bloodstream, with potential seeding of deep organs. The relative frequency of non-albicans species and resistance to antifungal drug classes vary by species and setting and influence how infections are studied.

Clinical relevance

Candidiasis ranges from common, self-limited surface infections to life-threatening bloodstream disease, and understanding the predisposing factors is part of clinical risk appraisal in infectious diseases. This entry summarises how the disease is categorised and studied; it is reference material and not a basis for individual diagnosis or therapy.

Epidemiology

Candida species are among the leading causes of healthcare-associated bloodstream infection, and invasive candidiasis carries substantial mortality. There has been a notable shift toward non-albicans species in many settings, accompanied by rising antifungal resistance; the multidrug-resistant species Candida auris has emerged as a global infection-control concern.

Evidence & guidelines

The Infectious Diseases Society of America maintains a clinical practice guideline for the management of candidiasis spanning mucocutaneous and invasive disease. Such guidance is updated periodically, and current versions should be consulted directly rather than relied upon from a summary.

History

Superficial Candida infection (thrush) has been recognised clinically for centuries, but invasive candidiasis rose to prominence in the later twentieth century with the growth of intensive care, indwelling vascular devices, broad-spectrum antibiotic use, and immunosuppression. More recently, the shift toward non-albicans species and the emergence of Candida auris have reshaped the epidemiology and the resistance landscape.

Debates

What is driving the shift toward non-albicans species and resistance?

Changes in patient populations, antifungal exposure, and species-specific resistance mechanisms have been associated with a relative rise in non-albicans Candida and reduced susceptibility, with implications for surveillance and stewardship that remain under study.

Seminal works

• pappas-2016
• pappas-2018
• pfaller-2007

Frequently asked questions

Is Candida always a pathogen?

No. Candida species are common commensals of the skin, gut, and mucosae; they cause disease mainly when local conditions or host defences shift in their favour.

What is the difference between thrush and invasive candidiasis?

Thrush refers to superficial mucosal candidiasis, such as oral or vulvovaginal infection, whereas invasive candidiasis involves the bloodstream (candidaemia) or deep organs and is far more serious.