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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. Candidiasis thereby 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, whereas superficial infections of skin and mucosal membranes by Candida causing local inflammation and discomfort is common in many human populations.    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. 
Additional recommended knowledge
In immunocompetent persons, candidiasis is usually a very localized infection of the skin or mucosal membranes :
Candidiasis is a very common cause of vaginal irritation, or vaginitis, and can also occur on the male genitals. In immunocompromised patients, the Candida infection can affect the esophagus with the potential of becoming systemic, causing a much more serious condition, a fungemia called candidemia.  
Children, mostly between the ages of 3 and 9 years, can be affected by chronic mouth yeast infections, normally seen around the mouth as white patches. However, this is not a common condition.
Candida yeasts are usually 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.
In a study of 1009 women in New Zealand, Candida 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. Pregnancy, the use of oral contraceptives, engaging in vaginal sex immediately and without cleansing after anal sex and using lubricants containing glycerin have been found to be causally related to yeast infections. Diabetes mellitus and the use of antibiotics are also linked to an increased incidence of yeast infections. Diet has been found to be the cause in some animals. Hormone Replacement Therapy and infertility treatments may also be predisposing factors.
A weakened or undeveloped immune system or metabolic illnesses, such as diabetes may predispose individuals to Candidiasis.  Diseases or conditions linked to candidiasis include HIV/AIDS, 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.  The former kills the good bacteria which would otherwise help maintain Candida at safe levels, thus allowing the fungus to overgrow.
Since the Candida fungus thrives in warm, moist and dark places, exposed areas with these conditions such as the mouth, skin folds, armpits and vaginas are more vulnerable and bad hygiene that fails to keep these areas clean will allow the Candida fungus to overgrow.
In penile candidiasis, the causes include sexual intercourse with an infected party, low immunity, antibiotics and diabetes. However, male yeast infection is less common and the risk of getting it is only a fraction of that in women.
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. Instead they had either bacterial vaginosis or a mixed-type infection.
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.
Medical professionals use two primary methods to diagnose yeast infections: microscopic examination, and culturing.
For the microscope method, 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 also placed on the slide. The KOH dissolves the skin cells but leaves the Candida untouched, so that when the slide is viewed under a microscope, the hyphae and pseudo spores of Candida are visible. Their presence in large numbers strongly suggests a yeast infection.
For the culturing method, a sterile swab is rubbed on the infected skin surface. The swab is then rubbed across a culture medium. The medium is incubated for several days, during which time colonies of yeast and/or bacteria develop. The characteristics of the colonies provide a presumptive diagnosis of the organism causing symptoms.
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.  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, 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.
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. Following the health tips at vulvovaginal health can help prevent vaginal candidiasis.
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
The genera Candida, species albicans was described by botanist Christine Marie Berkhout. She described the fungus 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).
The full current taxonomic classification is available at Candida albicans.
The genus Candida includes about 150 different species. However, only a few of those are known to cause human infections. C. albicans is the most significant pathogenic (=disease-causing) species. Other Candida species causing diseases in humans include C. tropicalis, C. glabrata, C. krusei, C. parapsilosis, C. dubliniensis, and C. lusitaniae.
Alternative medicine proponents frequently diagnose people with "systemic candidiasis" using methods not deemed valid by mainstream western medicine. Belief in widespread "systemic candidiasis" was promoted by a book published by Dr. William Crook, 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. Dr. Crook suggested a variety of remedies to treat these symptoms, ranging from dietary modification to colonic irrigation. Mainstream western medicine has ignored these alternatives, since they have not been proved using scientific methods. 
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Candidiasis". A list of authors is available in Wikipedia.|