fungal infection

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Several thousand species of fungi have been described, but fewer than 100 are routinely associated with invasive diseases of humans. In general, healthy humans have a very high level of natural immunity to fungi, and most fungal infections are mild and self-limiting. Intact skin and mucosal surfaces and a functional immune system serve as the primary barriers to colonization by these ubiquitous organisms, but these barriers are sometimes breached.

Unlike viruses, protozoan parasites, and some bacterial species, fungi do not require human or animal tissues to perpetuate or preserve the species. Virtually all fungi that have been implicated in human disease are free-living in nature. However, there are exceptions, including various Candida spp., which are frequently found on mucosal surfaces of the body such as the mouth and vagina, and Malassezia furfur, which is usually found on skin surfaces that are rich in sebaceous glands. These organisms are often cultured from healthy tissues, but under certain conditions they cause disease. Only a handful of fungi cause significant disease in healthy individuals. Once established, these diseases can be classified according to the tissues that are initially colonized.

Superficial mycoses

Four infections are classified in the superficial mycoses. Black piedra, caused by Piedraia hortai, and white piedra, caused by Trichosporn beigleii, are infections of the hair. The skin infections include tinea nigra, caused by Exophiala werneckii, and tinea versicolor, caused by M. furfur. Where the skin is involved, the infections are limited to the outermost layers of the stratum corneum; in the case of hairs, the infection is limited to the cuticle. In general, these infections cause no physical discomfort to the patient, and the disease is brought to the attention of the physician for cosmetic reasons.

Cutaneous mycoses

The cutaneous mycoses are caused by a homogeneous group of keratinophilic fungi termed the dermatophytes. Species within this group are capable of colonizing the integument and its appendages (the hair and the nails). In general, the infections are limited to the nonliving keratinized layers of skin, hair, and nails, but a variety of pathologic changes can occur depending on the etiologic agent, site of infection, and immune status of the host. The diseases are collectively called the dermatophytoses, ringworms, or tineas. They account for most of the fungal infections of humans.

Subcutaneous mycoses

The subcutaneous mycoses include a wide spectrum of infections caused by a heterogeneous group of fungi. The infections are characterized by the development of lesions at sites of inoculation, commonly as a result of traumatic implantation of the etiologic agent. The infections initially involve the deeper layers of the dermis and subcutaneous tissues, but they eventually extend into the epidermis. The lesions usually remain localized or spread slowly by direct extension via the lymphatics, for example, subcutaneous sporotrichosis.

Systemic mycoses

The initial focus of the systemic mycoses is the lung. The vast majority of cases in healthy, immunologically competent individuals are asymptomatic or of short duration and resolve rapidly, accompanied in the host by a high degree of specific resistance. However, in immunosuppressed patients the infection can lead to life-threatening disease. See also Fungi; Medical mycology.

Diseases caused by fungi which either digest dead tissue such as skin (e.g. athlete's foot) or parasitically feed on living tissue in the body (e.g. thrush). Fungal infections of the skin are usually characterized by itchy, red patches that may develop into pus-filled blisters. They tend to be very contagious and occur in warm, dark, moist regions of the body (e.g. in the groin). Primary treatment usually consists of washing with soap and water, drying thoroughly, and applying an antifungal agent. You are advised to consult a doctor if you suffer repeated or persistent fungal infections.

An infection caused by a fungus or yeast organism.

Definition

Fungi are types of parasitic plants that include molds, mildew, and yeast. A fungal infection is an inflammatory condition in which fungi multiply and invade the skin, the digestive tract, the genitals, and other body tissues, particularly, the lungs and liver. Fungal infections of the skin are often called ringworm or tinea.

Description

Microscopic fungi, which are called dermatophytes, often live exclusively on such dead body tissues as hair, the outer layer of the skin, and the nails. The fungus grows best in moist, damp, dark places with poor ventilation and on skin that is irritated, weakened, or continuously moist. Superficial fungal infections include tinea capitis, an infection of the neck and scalp; tinea barbae, also called barber's itch, along the beard area in adult males; tinea corporis on parts of the body, such as the arms, shoulders, or face; tinea cruris, or jock itch, involving the groin; tinea pedis, or athlete's foot; tinea versicolor; and tinea unguium, or infection of the nails. The term tinea gladiatorum is sometimes used to describe ringworm infections in atheletes. Tinea gladiatorum is most common in swimmers, wrestlers, and athletes involved in other contact sports. Fungal infections of the skin and nails are very common in children, but they can affect all age groups.

Systemic fungal infections occur when spores are touched or inhaled, or there is an overgrowth of fungi in or on the body. Such infections are most often a serious problem in those with suppressed immune systems. Candidiasis is a rather common fungal infection. When it occurs in the mouth, it is called thrush. Less often, it occurs in the mucous membranes of other parts of the digestive system, or in the vagina, heart valves, urinary tract, eyes, or blood. Other systemic fungal infections include aspergillosis, which mostly affects the lungs and may also spread to the brain and kidneys; blastomycosis, a lung infection that may spread through the bloodstream; coccidioidomycosis, also known as San Joaquin or valley fever; mucormycosis, which can develop into a very serious, life-threatening infection; and histoplasmosis.

Causes & Symptoms

Fungi are widespread in the environment, so it is not unusual that a certain amount of fungi and their spores end up being inhaled into the lungs or landing on the skin. Under conditions of moisture, warmth, irritation, or injury, these fungi grow rapidly and may cause illness. Superficial fungal infections may be due to an overgrowth of fungi already present, or the infection may be the result of contact with an infected person or with contaminated surfaces, bed sheets, towels, or clothing. Fungal infections can be spread from one part of the body to another by scratching or touching. Additionally, tinea unguium infections have been linked to the use of methyl methacrylate, a glue used for attaching acrylic fingernails.

Fungal spores are often present in soil and are likely to be inhaled when the soil is dug up or otherwise disturbed. Systemic fungal infections are commonly contracted in this way. In addition, fungi that normally inhabit the intestines, such as Candida albicans, may multiply, causing an infection due to an overgrowth of the fungi.

Tinea infections usually cause itchy, red, scaly, ring-shaped patches on the skin that spread easily. Hairs in the area of infection often fall out or break off, and the skin may crack. The skin may also develop a secondary bacterial infection. In tinea unguium, the nails discolor, crack, and thicken. Tinea versicolor may cause pigment changes in the skin that persist for up to a year.

Systemic fungal infections develop slowly. Symptoms often may be nonexistent, or there may be only the feeling of having a cold or the flu. Coughing, a fever, chest pain, chills, weight loss, and difficulty with breathing may become evident. Additional symptoms depend on the type and site of the infection.

Fungal infections are more common and more severe in people taking antibiotics, corticosteroids, immunosuppressant drugs, and contraceptives. This is also the case in people with endocrine disorders, immune diseases, and other conditions such as obesity, AIDS, tuberculosis, major burns, leukemia, and diabetes mellitus. Fungal infections often occur due to the use of antibiotic drugs for other conditions, because antibiotics kill off the bacteria that normally keep fungi at bay.

Diagnosis

Fungal infections of the skin, hair, and nails often can be diagnosed based on the characteristic appearance of affected areas. A KOH (potassium hydroxide) prep is a simple laboratory test to confirm the diagnosis. The test uses tissue samples treated with a 20% potassium hydroxide solution to detect fungi. Examining the skin with a Wood's ultraviolet lamp is another easy and convenient method to determine the presence of a fungus. Culture and sensitivity testing can be used if a more definitive diagnosis is required. Systemic fungal infections may be initially diagnosed from blood tests. Confirmation is determined by cultures made from sputum, blood, urine, bone marrow, or infected tissue samples.

Treatment

Among the herbs that slow down or halt the growth of fungus are goldenseal (Hydrastis canadensis), myrrh (Commiphora molmol), garlic (Allium sativa), pau d'arco (Tabeebuia impestiginosa), turmeric (Curcuma longa), oregano (Origanum vulgare), cinnamon (Cinnamonum zeylanicum), jewelweed, sage (Salvia officinalis), Impatiens aurea, yellow dock (Rumex crispus), the lichen known as old man's beard (Usnea barbata), black walnut husks and bark (Juglans nigra), licorice (Glycyrrhiza glabra), and Calendula officinalis. These herbs can be applied to external fungus as infusions, salves, powders, or vinegars. Many of them can also be taken internally as capsules or tinctures. Antifungal herbs can be quite strong, however, and care should be taken that a given remedy is suitable for internal use.

When an infusion is used, the affected area should be washed or soaked in the herbal water for at least 15 minutes twice daily. Store-bought or homemade tea bags can be soaked in water or vinegar for about 10 minutes and then used as a poultice for the same effect. Herbal vinegars make excellent remedies for fungus, as vinegar is in itself antifungal. "Gourmet" vinegars with such antifungal ingredients as oregano and garlic are often readily available at grocery stores. The vinegar can be applied a few times daily with cotton or compresses. In addition, a bentonite clay dusting powder can be useful for drying out the environment of moist skin in which fungus thrives. It works best when mixed with powdered antifungal herbs such as myrrh or goldenseal. Dusting powder is especially helpful for athlete's foot.

Many herbs high in essential oils also have antifungal action, particularly tea tree (Melaleuca alternifolia), oregano, lavender (Lavandula officinalis), Eucalyptus spp., rose geranium (Pelargonium graveolens), peppermint (Mentha piperita), chamomile (Matricaria recutita), and myrrh. Peppermint oil is especially helpful in relieving the itching associated with many fungal infections. The simplest way to use aromatherapy to fight fungal infections is to add several drops of any single essential oil or combination of oils to bathwater. Essential oil can also be added to mixtures for soaking or compresses. Tea tree is the herb most frequently recommended for the treatment of superficial fungal infections. As with all essential oils, the full-strength oil should be diluted in a carrier. A dilution of tea tree oil can be made by adding the essential oil to a carrier oil. This mixture can be added directly to the site of a skin infection.

A healthy diet should be maintained. Foods that are high in yeast, such as beer and wine, breads, and baked goods should be avoided. Fermented foods and sugary foods, including honey and fruit juices, should also be avoided until symptoms have cleared. Antifungal culinary herbs such as garlic, tumeric, oregano, sage, and cinnamon should be used liberally in foods. Yogurt containing live cultures can be incorporated into the diet to supply needed gut bacteria, and help reduce digestive infections such as candidiasis and thrush. Lactobacillus acidophilus and Lactobacillus bulgaricus can also be taken directly as supplements.

Supplements that can be taken for fungal infections include vitamins A, B complex, C, and E. Caprylic acid, an extract of the coconut plant, is also recommended as an antifungal, as well as grapefruit seed extract. Essential fatty acids, contained in evening primrose oil, fish liver oil, or flaxseed oil, can help reduce the inflammation of systemic or superficial fungal infections. A dose of one of these oils is recommended as a daily supplement.

Allopathic Treatment

Superficial fungal infections are usually treated with such antifungal creams or sprays as tolnaftate (Aftate or Tinactin), clotrimazole, miconazole nitrate (Micatin products), econazole, ketoconazole, ciclopirox, naftifine, itraconazole, terbinafine, fluconazole, or Whitfield's tincture made of salicylic acid and benzoic acid. If the infection is resistant, a doctor may prescribe an oral antifungal drug such as ketoconazole or griseofulvin. Drugs used for systemic infections include amphotericin B, which is highly toxic and is used for severe or life-threatening infections; the azoles, particularly fluconazole and itraconazole, which have been found to be the least toxic of these medications; and flucytosine alone or in combination with other antifungal medications. Fungal infections that become inflamed may be treated with a combination antifungal/steroid medication. Certain infections may require surgery.

Expected Results

Infections usually respond to treatment within several weeks. However, many fungal infections are resistant to treatment, and it may take an extended time and repeated treatments to effect a cure. Infections may spread, and secondary bacterial infections may develop. Medications for fungal infections are often strong, and their use may cause such undesirable side effects as headache, dizziness, nausea, vomiting, or abdominal pain. Fungal infections are usually not serious in otherwise healthy individuals. However, a systemic fungal infection may be severe and life-threatening for those with compromised immune systems.

Prevention

Good personal hygiene should be maintained. In the case of superficial infections, the skin should be kept clean and dry, and care should be taken to avoid contact with other parts of the body. If someone in the household has a superficial fungal infection, bed sheets, towels, floors, shower stalls, and other contact surfaces should be washed with hot water and disinfected after use.

Resources

Books

Duke, James A., Michael Castleman, and Alice Feinstein. The Green Pharmacy. Emmaus, PA: Rodale Press, 1997.

Periodicals

Farschian, M., R. Yaghoobi, and K. Samadi. "Fluconazole Versus Ketoconazole in the Treatment of Tinea Versicolor." Journal of Dermatologic Treatment 13 (June 2002): 73-76.

Kohl, T. D., et al. "Tinea gladiatorum: Pennsylvania's Experience." Clinical Journal of Sports Medicine 12 (May 2002): 165-171.

Lipozencic J., M. Skerlev, R. Orofino-Costa et al. "A Randomized, Double-Blind, Parallel-Group, Duration-Finding Study of Oral Terbinafine and Open-Label, High-Dose Griseofulvin in Children with Tinea Capitis Due to Microsporum Species." British Journal of Dermatology 146 (May 2002): 816-823.

Weinstein, A., and B. Berman. "Topical Treatment of Common Superficial Tinea Infections." American Family Physician 65 (May 15, 2002): 2095-2102.

Organizations

American Academy of Dermatology. 930 East Woodfield Rd., PO Box 4014, Schaumburg, IL 60168. (847) 330-0230. .

Other

drkoop.com Medical Encyclopedia. "Ringworm." http://www.drkoop.com/conditions/ency/article/001439.htm.

Merck & Co., Inc. The Merck Manual of Diagnosis and Therapy.http://www.merck.com/pubs/mmanual/section10/chapter113/113a.htm.

Merck & Co., Inc. The Merck Manual of Diagnosis and Therapy.http://www.merck.com/pubs/mmanual/section13/chapter158/158a.htm.

[Article by: Patience Paradox; Rebecca J. Frey, PhD]

Fungal infections of the skin are among today's most common infectious diseases, and they occur worldwide. Superficial fungus infections fall into three broad categories: the dermatophytes (ringworm), tinea versicolor, and cutaneous candidiasis (yeast infection).

Tinea Corporis (Ringworm of the Skin). The typical lesion is an itchy, round or oval patch of skin with central clearing and a red scaly margin— hence the name "ringworm." If it occurs in the groin, it is called "jock itch" or "tinea cruris." If there are only two or three rings of infection, topical therapy with antifungal creams will be sufficient. For widespread infection, oral antifungal pills may be necessary.

Tinea Capitis (Fungal Infection of the Hair). Fungal infections of the scalp are most common in children. The infection presents as round scaly patches of hair loss, often with broken-off stubbly hairs. The infection must be treated with oral antifungal therapies. The prognosis is excellent and shaving the scalp is not necessary.

Tinea Pedis (Fungus of the Feet, or Athlete's Foot). Tinea pedis is the most common type of fungal infection, presenting as itchy, scaling, and/or macerated webspaces. There may be a powdery white scaling of the bottom of the feet. Sometimes the infection presents as blisters on the bottom of the feet. The infection can spread to the groin (tinea cruris). Topical antifungals will cure the webspace infections but oral antifungals are necessary to treat the blistering infections. Afflicted individuals should keep their feet dry and spray their shoes with antifungal sprays.

Tinea of the Nails (Onychomycosis). Toenails are more commonly affected than fingernails. The nail becomes opaque, yellowish, thickened, and crumbly with the accumulation of material under the nail. There may be an associated athlete's foot infection. Oral antifungals are necessary to cure the problem.

Candidiasis (Yeast Infections). Yeast infections occur in closed spaces on the skin, such as the corner of the mouth, under breasts, in armpits, and in the groin. It is a red, moist, and often odorous tender rash, and is more severe in patients taking antibiotics or who have systemic diseases such as diabetes. Heat and sweat aggravate the problem. Candidiasis can also occur in the mouth (oral thrush) or as a yeast vaginitis. Treatment is with topical antiyeast creams and/or oral medication. To prevent recurrence, the area must be kept dry.

Tinea Versicolor. Tinea versicolor presents on the upper trunk—as brown spots in the winter and white spots in the summer. It is easily treated by washing the area with antidandruff shampoos, but the therapy must be repeated monthly to prevent recurrence.

— SUSAN SWIGGUM; JOHN ADAM

Disease such as athlete's foot and dhobie itch, which are caused by a fungus. Fungi thrive in damp, warm, unclean environments. Infections can be prevented by keeping the skin dry and scrupulously clean. Antifungicides (e.g. miconazole cream) can be used to treat acute infections.

An infection caused by fungi, such as athlete's foot and chlamydia. (See under “Life Sciences.”)