Candidiasis

Candidiasis Classification and external resources
Agar plate culture of Candida albicans
ICD-10	B37.
ICD-9	112
DiseasesDB	1929
MedlinePlus	001511
eMedicine	med/264  emerg/76 ped/312 derm/67
MeSH	D002177

Candidiasis, commonly called yeast infection or thrush, is a fungal infection (mycosis) of any of the Candida species, of which Candida albicans is the most common.^[1][2] Candidiasis encompasses infections that range from superficial, such as oral thrush and vaginitis, to systemic and potentially life-threatening diseases. Candida infections of the latter category are also referred to as candidemia and are usually confined to severely immunocompromised persons, such as cancer, transplant, and AIDS patients.

Superficial infections of skin and mucosal membranes by Candida causing local inflammation and discomfort are however common in many human populations.^[2][3][4] While clearly attributable to the presence of the opportunistic pathogens of the genus Candida, candidiasis describes a number of different disease syndromes that often differ in their causes and outcomes.^[2][3]

Manifestations

Most candidial infections are treatable and result in minimal complications such as redness, itching and discomfort, though complication may be severe or fatal if left untreated in certain populations. In immunocompetent persons, candidiasis is usually a very localized infection of the skin or mucosal membranes, including the oral cavity (thrush), the pharynx or esophagus, the gastrointestinal tract, the urinary bladder, or the genitalia (vagina, penis).^[1]

Candidiasis is a very common cause of vaginal irritation, or vaginitis, and can also occur on the male genitals. In immunocompromised patients, Candida infections can affect the esophagus with the potential of becoming systemic, causing a much more serious condition, a fungemia called candidemia.^[4][3]

Children, mostly between the ages of three and nine years of age, can be affected by chronic mouth yeast infections, normally seen around the mouth as white patches. However, this is not a common condition.

Causes

Oral candidiasis on the tongue and soft palate.

Candida yeasts are commonly present in most people, but uncontrolled multiplication resulting in disease symptoms is kept in check by other naturally occurring microorganisms, e.g., bacteria co-existing with the yeasts in the same locations, and by the human immune system.^[5]

In a study of 1009 women in New Zealand, C. albicans was isolated from the vaginas of 19% of apparently healthy women. Carriers experienced few or no symptoms. However, external use of irritants (such as some detergents or douches) or internal disturbances (hormonal or physiological) can perturb the normal flora, constituting lactic acid bacteria, such as lactobacilli, and an overgrowth of yeast can result in noticeable symptoms.^[6] Pregnancy and the use of oral contraceptives have been reported as risk factors,^[7] while the roles of engaging in vaginal sex immediately and without cleansing after anal sex and using lubricants containing glycerin remain controversial. Diabetes mellitus and the use of antibiotics are also linked to an increased incidence of yeast infections.^[7] Diet has been found to be the cause in some animals;^[8] Hormone Replacement Therapy and infertility treatments may also be predisposing factors.^[9]

A weakened or undeveloped immune system or metabolic illnesses such as diabetes may predispose individuals to candidiasis.^[10] Diseases or conditions linked to candidiasis include HIV/AIDS, mononucleosis, cancer treatments, steroids, stress, and nutrient deficiency, among many others. Almost 15% of people with weakened immune systems develop a systemic illness caused by Candida species. In extreme cases, these superficial infections of the skin or mucous membranes may enter into the bloodstream and cause systemic Candida infections.

Antibiotic and steroid use are the most common reason for yeast overgrowth.^[11] The former kills the bacteria which would otherwise help maintain Candida at safe levels, thus allowing the fungus to overgrow.

In penile candidiasis, the causes include sexual intercourse with an infected party, low immunity, antibiotics, and diabetes. Male genital yeast infection is less common, and the risk of getting it is only a fraction of that in women; however, yeast infection on the penis from direct contact via sexual intercourse with an infected partner is not uncommon.^[12]

Symptoms

Symptoms include severe itching, burning, and soreness, irritation of the vagina and/or vulva, and a whitish or whitish-gray discharge, often with a curd-like appearance. Many women mistake the symptoms of the more common bacterial vaginosis for a yeast infection. In a 2002 study published in the Journal of Obstetrics and Gynecology, only 33 percent of women who were self-treating for a yeast infection actually had a yeast infection, while most had either bacterial vaginosis or a mixed-type infection instead.

In men, symptoms include red patchy sores near the head of the penis or on the foreskin, severe itching, and/or a burning sensation. Candidiasis of the penis can also have a white discharge, although uncommon. However, having no symptoms at all is common, and usually, a more severe form of the symptoms may emerge later.

Diagnosis

Micrograph of esophageal candidiasis. Biopsy specimen; PAS stain.

Medical professionals may use two primary methods to diagnose yeast infections: microscopic examination and culturing.

For identification by light microscopy, a scraping or swab of the affected area is placed on a microscope slide. A single drop of 10% potassium hydroxide (KOH) solution is then added to the specimen. The KOH dissolves the skin cells but leaves the Candida cells intact, permitting visualization of hyphae and yeast cells typical of many Candida species.

For the culturing method, a sterile swab is rubbed on the infected skin surface. The swab is then streaked on a culture medium. The culture is incubated at 37 °C for several days, to allow development of yeast or bacterial colonies. The characteristics (such as morphology and colour) of the colonies may allow initial diagnosis of the organism that is causing disease symptoms.

Treatment

It is important to consider that Candida species are frequently part of the human body's normal oral and intestinal flora. Treatment with antibiotics can lead to eliminating the yeast's natural competitors for resources, and increase the severity of the condition.

In clinical settings, candidiasis is commonly treated with antimycotics—the antifungal drugs commonly used to treat candidiasis are topical clotrimazole, topical nystatin, fluconazole, and topical ketoconazole. For example, a one-time dose of fluconazole (as Diflucan 150-mg tablet taken orally) has been reported as being 90% effective in treating a vaginal yeast infection.^[13] This dose is only effective for vaginal yeast infections, and other types of yeast infections may require different treatments. In severe infections (generally in hospitalized patients), amphotericin B, caspofungin, or voriconazole may be used. Local treatment may include vaginal suppositories or medicated douches. Gentian violet can be used for breastfeeding thrush, but pediatrician William Sears recommends using it sparingly,^[14] since in large quantities it can cause mouth and throat ulcerations in nursing babies, and has been linked to mouth cancer in humans and to cancer in the digestive tract of other animals.^[15]

While home remedies may offer relief in minor cases of infection, seeking medical attention may be necessary, especially if the extent of the infection cannot be judged accurately by the patient. For instance, oral thrush is visible only at the upper digestive tract, but it may be that the lower digestive tract is likewise colonized by Candida species.

Treating candidiasis solely with medication may not give desired results, and other underlying causes require consideration. For example, oral candidiasis can also be the sign of a more serious condition, such as HIV infection or other immunodeficiency diseases. Maintaining vulvovaginal health can help prevent vaginal candidiasis.

It is possible for Candida Albicans to develop a resistance to the drugs used to treat it, as seen from research done^[16] involving fluconazole, one of the drugs that is used to treat candidiasis. In this case, the recurring infection would have to use a different prescription, and it is possible that resistance is slowly built to many of the available medications used to treat the yeast infection.

Babies with diaper rash should have their diaper areas kept clean, dry, and exposed to air as much as possible. Sugars assist the overgrowth of yeast, possibly explaining the increased prevalence of yeast infections in patients with diabetes mellitus, as noted above. As many Candida spp. reside in the digestive tract, dietary changes may be effective for preventing or during a Candida infection. Due to its requirement for readily-fermentable carbon sources, such as mono- or dimeric sugars (e.g., sucrose, glucose, lactose) and starch, avoiding foods that contain these nutrients in high abundance may help to prevent excessive Candida growth.

History and taxonomic classification

See also: Candida albicans

The genus Candida and species albicans was described by botanist Christine Marie Berkhout in her doctoral thesis at the University of Utrecht in 1923. Over the years, the classification of the genera and species has evolved. Obsolete names for this genus include Mycotorula and Torulopsis. The species has also been known in the past as Monilia albicans and Oidium albicans. The current classification is nomen conservandum, which means the name is authorized for use by the International Botanical Congress (IBC).^[17]

The genus Candida includes about 150 different species, however, only a few are known to cause human infections: C. albicans is the most significant pathogenic species. Other Candida species pathogenic in humans include C. tropicalis, C. glabrata, C. krusei, C. parapsilosis, C. dubliniensis, and C. lusitaniae.

Alternative views

Some alternative medicine proponents postulate a widespread occurrence of "systemic candidiasis". The view was promoted in a book published by Dr. William Crook,^[18] which hypothesized that a variety of common symptoms such as fatigue, PMS, sexual dysfunction, asthma, psoriasis, digestive and urinary problems, multiple sclerosis, and muscle pain, could be caused by subclinical infections of Candida albicans. Crook suggested a variety of remedies to treat these symptoms, ranging from dietary modification to colonic irrigation. With the exception of the few dietary studies in the urinary tract infection section conventional medicine has not used most of these alternatives, since there is limited scientific evidence to prove their effectiveness, or that subclinical "systemic candidiasis" is a viable diagnosis.^[19][20]

References

External links

• National Institute of Allergies and Infections (2007-06-27). "Vaginitis". Retrieved on 2008-02-21.: Fact sheet on vaginitis/vaginal infections

• Candidiasis at eMedicine

• Oral Thrush Mayo Clinic

Images

• DermAtlas candidiasis images
• Links to pictures of Yeast Infection (Hardin MD/Univ of Iowa)