29th July 2023

Candidiasis

Candidiasis refers to the infection caused by yeasts belonging to the genus Candida. Candida albicans causes the majority of candidiasis. However, a range of non-albicans Candida species have been associated with human infection (e.g. Candida glabrata, Candida tropicalis, Candida parapsilosis and Candida krusei).

Candida are commensal organisms of the skin, oropharynx, gastrointestinal tract, and vagina. Overgrowth in these sites (e.g. following antibiotic therapy disrupting the local bacterial microbiota) can cause local or superficial infection. More invasive or disseminated infection typically occurs in cases of severe immunosuppression (e.g. neutropenia, particularly within haematological malignancy), indwelling prosthetic material (e.g. intravascular catheters), or heavy inoculation of a usually sterile site (e.g. following perforation of the gastrointestinal tract).

The major clinical manifestations of candida are discussed below.

Vulvovaginal candidiasis

Also known as genital thrush, vulvovaginal candidiasis presents as localised inflammation of the vagina or vulva. Around 90% of cases are due to Candida albicans. It is a common condition that can affect any person with female genitalia, regardless of age. It is generally due to the overgrowth of commensal candida and is strongly associated with antibiotic therapy leading to disruption to the balance of natural vaginal flora.

Other risk factors for vulvovaginal candidiasis include oestrogen excess (e.g. pregnancy. HRT), use of local irritants such as soaps and douches, and immunocompromise (see below).

Acute infection refers to an isolated infection. Recurrent candida is defined as 4 or more symptomatic episodes in 1 year, and can indicate an underlying disease causing immunosuppression; hence warrants investigation for diabetes mellitus and HIV. Long-term steroid use is also associated with recurrent candida due to immunosuppression.

Diagnosis can generally be made clinically, and if the diagnosis is apparent from the history, an external examination may not be indicated. However, this should be done if the diagnosis is uncertain, and if laboratory confirmation is required, then high-vaginal swabs and cultures are the main diagnostic test. STI screening may also be indicated.

For acute infection, management includes symptomatic measures such as emollients, avoiding irritants like soap, and wearing loose-fitting clothing. The drug treatment of choice is single dose oral fluconazole or single dose clotrimazole, pessary if fluconazole is contraindicated. Vulval disease can be co-treated with topical or intravaginal clotrimazole, which is available over the counter.

For recurrent infection, an induction dose of 3 doses of oral fluconazole is given, followed by a 6 month course of once-weekly doses, with appropriate follow up arranged.

Oral fluconazole is not recommended in pregnancy – topical or intravaginal formulations are used instead.

Oropharyngeal candidiasis

‘Oral thrush’ is another common form of candidiasis. In addition to the general risk factors for candidiasis, poor dental hygiene, smoking, malnutrition, and those with dental prostheses are an additional risk.

The most common form is pseudomembranous oral candidiasis, which presents with distinctive white-yellow plaques in the oral cavity. Unlike diseases like leukoplakia, these can be easily removed, which is an important distinguishing factor. Diagnosis is generally clinical, and swabs are not required.

In a non-immunocompromised individual, 2 weeks of treatment with a topical antifungal, such as miconazole gel or Nystatin, is recommended. Oral fluconazole can be used in severe cases.

In immunocompromised patients, the first line treatment is the same, but there is a higher risk of recurrent infection, spread to the oesophagus, or systemic infection, so the patient should be closely monitored for these complications.

Oesophageal candidiasis

A more serious manifestation, which may occur as a complication of oropharyngeal candidiasis, is generally only seen in immunocompromised patients, especially those with HIV and on chemotherapy.

Clinical features include dysphagia, pain on swallowing (odynophagia), and retrosternal pain; although it may be asymptomatic. Odynophagia is considered the hallmark feature, and oesophageal candidiasis should be considered in any immunosuppressed patient reporting this symptom.

The characteristic plaques generally cannot be visualised; hence, endoscopy is required, from which histological samples may be sent.

Systemic treatment should be given – oral fluconazole for a minimum of 2 weeks is first line, although it may need to be given IV if this cannot be tolerated. Itraconazole and voriconazole can be used as second line options.

Candidaemia

This refers to the presence of Candida in the bloodstream as septicaemia and is associated with severe disseminated illness. It may occur as a complication of localised infection and is generally only seen in immunocompromised patients. Invasive candidiasis refers to systemic infection but may or may not be associated with candidemia. Sites that may be affected by invasive candidiasis include the CNS, heart (i.e. endocarditis), bones, joints, abdomen, renal tract, and eyes.

This is a severe life-threatening illness that necessitates hospital management and parental treatment. The echinocandin caspofungin given IV is the first line, and IV fluconazole may also be used. Liposomal amphotericin B can be used in refractory cases.