Candida

Candida refers to infection by the fungus Candida albicans, also known as thrush, yeast infection or moniliasis. Candidiasis affects areas of mucous membrane in the body, most commonly the vagina and the inside of the mouth. In infants, candidiasis can occur in conjunction with nappy rash.

Causes

The fungus is normally present in the mouth and the vagina, but in some situations it may multiply excessively. Candidiasis may occur if antibiotic drugs destroy the harmless bacteria that control the growth of the fungus, or if the body’ s resistance to infection is lowered. Certain disorders, for example diabetes mellitus, and the hormonal changes that occur during pregnancy or with oral contraceptives, may also encourage growth of the fungus. Candidiasis can be contracted by having sexual intercourse with an infected partner. The infection is far more common in women than in men.

Symptoms

Symptoms of vaginal infection include a thick, white discharge, genital irritation, and discomfort on passing urine. Less commonly, the penis is infected, usually causing balanitis (inflammation of the head of the penis). Oral candidiasis produces sore, white or creamy-yellow, raised patches inside the mouth. Candidiasis may spread from the genitals or mouth to other moist areas of the body. It may also affect the gastrointestinal tract, especially in people with impaired immune systems, such as those taking immunosuppressant drugs or who have HIV (the virus that leads to AIDS).

Diagnosis and Treatment

Candidiasis is diagnosed by examination of a sample taken from the white discharge or from patches. The condition is treated topically with antifungal drugs such as clotrimazole or with oral antifungals. The drugs are given in the form of creams, vaginal pessaries, or throat lozenges. Treatment of candidiasis is usually successful, but the condition may recur. Some people are troubled by persistent and frequently recurrent yeast infections.

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Candida Infection in more detail - technical medical article

Superficial candidosis (candidiasis)

Aetiology

Superficial candidosis is a term used to describe a group of infections of skin or mucous membranes caused by species of the genus Candida. They range in severity from oral thrush to chronic mucocutaneous candidosis, a chronic infection refractory to conventional antifungal treatment.

Candida albicans is the species most frequently involved. It is a saprophytic yeast often found as a commensal in the mouth and gastrointestinal tract, and is commonly present in the vagina. Several factors may influence the incidence of carriage. For instance, oral colonization is more common in hospital staff than in equivalent nonhospital employees. Vaginal carriage is more common in pregnancy. Other factors (Box 1) are known that predispose to conversion from a commensal to a parasitic role with the causation of disease—candidosis. The list includes factors that influence host immunological response, such as carcinoma, AIDS, or cytotoxic therapy; those that disturb the population of other microorganisms, such as antibiotics; and those that affect the character of the epithelium, such as dentures.

Box 1 Predisposing factors in superficial candidosis

  • ◆ Local epithelial defects, occlusion, constant immersion in water, e.g. damaged nail folds, beneath dentures
  • ◆ Defects of immunity (primarily T cell or phagocytosis)
    • • Primary immunological disease, e.g. chronic granulomatous disease
    • • Immunodefects secondary to intercurrent illness, e.g. leukaemia
    • • Immunodefects secondary to therapy, e.g. cytotoxic therapy in organ transplantation
  • ◆ Drug therapy, e.g. antibiotics
  • ◆ Carcinoma or leukaemia
  • ◆ Endocrine disease
    • • Diabetes mellitus
    • • Hypothyroidism, hypoparathyroidism, hypoadrenalism (all in chronic mucocutaneous candidosis)
  • ◆ Physiological changes, e.g. infancy, pregnancy, old age
  • ◆ Miscellaneous disorders, e.g.
    • • Iron deficiency
    • • Zinc deficiency
    • • Malabsorption

Other species of candida may also cause superficial infections, but are less common. They include C. glabrata, C. dubliniensis, and C. parapsilosis. There is evidence that the first two species are more common in oral infection in patients with HIV and C. glabrata in vaginal candidosis.

Epidemiology

Superficial candida infections are seen in all countries.

Clinical features

There are a number of clinically distinct types of superficial infection caused by candida species, as follows.

Oral candidosis (thrush)

Oral infection by candida is fairly common, particularly in infancy and old age, or in association with antibiotic or cytotoxic therapy, or in diseases where the neutrophil or T-lymphocyte responses may be impaired. In older people, the wearing of dentures is a predisposing factor. The lesions present with discomfort both in the mouth and at the corners of the lips. The mouth and buccal mucosa show patchy or confluent, white adherent plaques; less commonly the mucosa and tongue are sore and glazed—erythematous candidosis. Angular cheilitis usually accompanies the oral lesions. In long-standing cases, the plaque may become hypertrophic, with oedema of the mucosal surfaces, or the mucosa may appear glazed and raw.

There is a significant correlation between leucoplakia and oral candidosis, and it has been suggested that the infection may lead to epithelial dysplasia.

The diagnosis is made by the demonstration of yeasts and hyphae of candida in smears, and by culture.

Vaginal candidosis (thrush)

Vulvovaginal candidiasis

About 75% of women will at some time in their lives develop vulvovaginal candidiasis or ‘yeast infections’. C. albicans causes 90 to 95% of vulvovaginal candidiasis; of the many other species of yeast that are sometimes implicated, C. glabrata is thought to be the second most common. Commonly recognized risk factors for candidiasis include the use of oral contraceptives, recent use of broad-spectrum antimicrobials, pregnancy, diabetes mellitus, and immunosuppression. Being sexually active and practising oral receptive sex are associated with vulvovaginal candidiasis, but there are no data to support partner treatment. Patients with vulvovaginal candidiasis complain primarily of vulvar or vaginal pruritus, irritation, burning, dyspareunia, or abnormal discharge. The symptom of discharge is quite unreliable in predicting which women with vaginitis actually have vulvovaginal candidiasis. Examination of affected women may reveal vulvar erythema, oedema, excoriations, or fissures. Vaginal thrush may be present. The vaginal pH is normal. On microscopy, hyphae or blastospores may be seen, but the sensitivity is fairly low (c.50%); thus, a simple yeast culture is recommended in women who are symptomatic but with negative microscopy.

For most women with vulvovaginal candidiasis, the infection will be uncomplicated: it is sporadic, associated with relatively mild symptoms, caused by C. albicans, and is occurring in an otherwise normal host. Uncomplicated vulvovaginal candidiasis generally responds readily to any available antimycotic treatment. Topical therapies consist primarily of imidazoles, including miconazole, clotrimazole, butoconazole, and terconazole, which are available as creams or suppositories applied for 1 to 7 days. A single150-mg dose of oral fluconazole seems equivalent to topical treatments.

An estimated 5% will suffer complicated vulvovaginal candidiasis, marked by either an underlying medical problem such as diabetes mellitus or HIV infection, severe symptoms, recurrent disease (four or more episodes per year), or an infection caused by a yeast other than C. albicans. Most of these women will not have any of the commonly recognized risk factors for infection. Complicated vulvovaginal candidiasis will recur within a month in at least 50% of cases, and is best managed by first obtaining a positive yeast culture to obtain information about the species of the isolate, then by more aggressive therapy and follow-up. In patients with severe vulvovaginal candidiasis, a second dose of fluconazole 3 days after the first, or a second week of topical therapy, improves the chance of complete resolution. Women with recurrent vulvovaginal candidiasis caused by C. albicans benefit from prolonged suppressive therapy with weekly oral fluconazole (100–200 mg) after an initial induction phase of 3 doses given 3 days apart. Finally, for C. glabrata infections, boric acid capsules (600 mg vaginally), nightly for 14 days, are often curative.

Paronychia

Infection around the nail fold is seen in people whose occupations involve frequent wetting of the hands (such as cooks) or in those with eczema or psoriasis. The aetiology is complicated and there may be a mixture of bacterial infection and irritant or allergic contact dermatitis as well as candida infection. The condition presents with painful, red swelling of the nail fold. Pus may be discharged. Secondary invasion of the lateral border of the nail plate by candida may occur from this site.

Candida intertrigo

Infection of the moist folds of the skin in the groin or under the breasts causes itching and discomfort. The area becomes macerated and erythematous. Candida may contribute to this condition, but is certainly not the only factor. It may also superinfect the napkin area in infants. The presence of satellite pustules (see above) is a useful indicator of involvement by candida in the disease process.

Direct invasion of toe-web folds by candida closely resembles ‘athlete’s foot’ caused by dermatophytes. A similar erosive infection may occur in the finger webs—interdigital candidosis—and is seen most commonly in the tropics.

Chronic superficial candidosis

Chronic candida infections of the mouth, vagina, and nail present problems in management. Chronic oral candidosis, for instance, is associated with leucoplakia. Predisposing causes should be searched for. The most serious of this group of infections is chronic mucocutaneous candidosis, a rare condition in which chronic skin, nail, and mucosal infection coexist. A series of underlying genetic, endocrine (hypoparathyroidism, hypoadrenalism, or hypothyroidism), and immunological abnormalities has been found; in some cases it has been associated with mutations in an autoimmune regulator gene (AIRE). Extensive human papillomavirus (wart) or dermatophyte infections may also be present in these patients, whose condition is normally diagnosed in childhood.

Oral candidosis is one of the earliest signs of untreated AIDS, occurring in a high proportion of patients. The appearances are similar to those seen with other groups, although plaque formation may be very extensive. Oesophageal infection is common in this group.

Laboratory diagnosis

All these infections are diagnosed by microscopy and culture. When associated with the condition, candida cells are always evident on microscopy. Culture establishes the specific identity and is important particularly where species other than Candida albicans may be involved.

Treatment

Two groups of drugs are effective in superficial candidosis. The polyenes such as nystatin and amphotericin B are topically active in many forms of candidosis. They are often less effective in oral candidosis in immunodeficient patients, including those with AIDS. Likewise, topical azole drugs such as miconazole and clotrimazole are usually effective in superficial candidosis. For unresponsive cases, oral therapy with fluconazole, itraconazole, or ketoconazole may be necessary. Fluconazole resistance can occur and C. glabrata is seldom responsive to this drug.

For vaginal infections, topical creams or vaginal preparations should be used—many requiring only a single treatment. Single-dose oral fluconazole is an alternative. In recalcitrant cases it may be necessary to use longer courses of fluconazole or itraconazole.