Fungal (Mycotic) Infections
Fungi, tiny members of a subdivision of the plant kingdom that feed on organic matter, are responsible for various common skin infections. In some cases, they affect only the skin and its ap-pendages (ie, hair and nails). In other cases, the internal organs are involved, and this disease may be life-threatening. Superficial infections, however, rarely cause even temporary disability and respond readily to treatment. Secondary infection with bacteria, Candida, or both organisms may occur.
The most common fungal skin infection is tinea, which is also called ringworm because of its characteristic appearance of ring or rounded tunnel under the skin. Tinea infections affect the head, body, groin, feet, and nails. Table 56-6 summarizes the tinea in-fections.
To obtain a specimen for diagnosis, the lesion is cleaned, and a scalpel or glass slide is used to remove scales from the margin of the lesion. The scales are dropped onto a slide to which potassium hydroxide has been added. The diagnosis is made by examination of the infected scales microscopically for spores and hyphae or by isolating the organism in culture. Under Wood’s light, a speci-men of infected hair appears fluorescent; this may be helpful in diagnosing some cases of tinea capitis.
Tinea pedis (ie, athlete’s foot) is the most common fungal infec-tion. It is especially prevalent in those who use communal show-ers or swimming pools (Odom et al., 2000).
Tinea pedis may appear as an acute or chronic infection on the soles of the feet or between the toes. The toenail may also be involved. Lymphangitis and cellulitis occur occasionally when bacterial superinfection occurs. Sometimes, a mixed infection in-volving fungi, bacteria, and yeast occurs.
During the acute, vesicular phase, soaks of Burow’s solution or potassium permanganate solutions are used to remove the crusts, scales, and debris and to reduce the inflammation. Topical anti-fungal agents (eg, miconazole, clotrimazole) are applied to the in-fected areas. Topical therapy is continued for several weeks because of the high rate of recurrence.
Footwear provides a favorable environment for fungi, and the causative fungus may be in the shoes or socks. Because moisture encourages the growth of fungi, the patient is instructed to keep the feet as dry as possible, including the areas between the toes.
Small pieces of cotton can be placed between the toes at night to absorb moisture. Socks should be made of cotton, and hosiery should have cotton feet, because cotton is an effective absorber of perspiration.
For people whose feet perspire excessively, perforated shoes permit better aeration of the feet. Plastic- or rubber-soled footwear should be avoided. Talcum powder or antifungal powder applied twice daily helps to keep the feet dry. Several pairs of shoes should be alternated so that they can dry completely before being worn again.
In tinea corporis (ie, ringworm of the body), the typical ringed le-sion appears on the face, neck, trunk, and extremities (Fig. 56-3). Animal (nonhuman) varieties are known to cause an intense in-flammatory reaction in humans because they are not adapted to living on human hosts. Humans make contact with animal va-rieties through contact with pets or objects that have been in contact with an animal.
Topical antifungal medication may be applied to small areas. Oral antifungal agents are used only in extensive cases. Side ef-fects of oral antifungal agents include photosensitivity, skin rashes, headache, and nausea. Newer antifungal agents, including itra-conazole, fluconazole, and terbinafine, have been more effective with fewer systemic side effects than griseofulvin in patients with chronic fungal (dermatophyte) infections.
The patient is instructed to use a clean towel and washcloth daily. Because fungal infections thrive in heat and moisture, all skin areas and skin folds that retain moisture must be dried thor-oughly. Clean cotton clothing should be worn next to the skin.
Ringworm of the scalp is a contagious fungal infection of the hair shafts and a common cause of hair loss in children. Any child with scaling of the scalp should be considered to have tinea capi-tis until proven otherwise. Clinical examination reveals one or several round, red scaling patches. Small pustules or papules may be seen at the edges of such patches.
As the hairs in the affected areas are invaded by the fungi, they become brittle and break off at or near the surface of the scalp, leaving bald patches or the clas-sic sign of black dots, which are the broken ends of hairs. Because most cases of tinea capitis heal without scarring, the hair loss is only temporary.
Griseofulvin, an antifungal agent, is prescribed for patients with tinea capitis. Topical agents do not provide an effective cure be-cause the infection occurs within the hair shaft and below the surface of the scalp. However, topical agents can be used to in-activate organisms already on the hair. This minimizes contagion and eliminates the need to clip the hair. Infected hairs break off anyway, and noninfected ones may remain in place. The hair should be shampooed two or three times weekly, and a topical anti-fungal preparation should be applied to reduce dissemination of the organisms.
Because tinea capitis is contagious, the patient and family should be instructed to set up a hygiene regimen for home use. Each per-son should have a separate comb and brush and should avoid ex-changing hats and other headgear. All infected members of the family must be examined because familial infections are relatively common. Household pets should also be examined.
Tinea cruris (ie, jock itch) is ringworm infection of the groin, which may extend to the inner thighs and buttock area. It occurs most frequently in young joggers, obese people, and those who wear tight underclothing. The incidence of tinea cruris is in-creased among people with diabetes.
Mild infections may be treated with topical medication such as clotrimazole, miconazole, or terbinafine for at least 3 to 4 weeks to ensure eradication of the infection. Oral antifungal agents may be required for more severe infections. Heat, friction, and mac-eration (from sweating) predispose the patient to the infection. The nurse instructs the patient to avoid excessive heat and hu-midity as much as possible and to avoid wearing nylon under-wear, tight-fitting clothing, and a wet bathing suit. The groin area should be cleaned, dried thoroughly, and dusted with a topical antifungal agent such as tolnaftate (Tinactin) as a preventive mea-sure, because the infection is likely to recur.
Tinea unguium (ie, ringworm of the nails) is a chronic fungal in-fection of the toenails or, less commonly, the fingernails. It is usu-ally caused by Trichophyton species (T. rubrum, T. mentagrophytes) or Candida albicans. It is usually associated with long-standing fungal infection of the feet. The nails become thickened, friable (ie, easily crumbled), and lusterless. In time, debris accumulates under the free edge of the nail. Ultimately, the nail plate separates. Because of the chronicity of this infection, the entire nail may be destroyed.
An oral antifungal agent is prescribed for 6 weeks when the fin-gernails are involved and 12 weeks when the toenails are involved. Selection of the antifungal agent depends on the causative fun-gus. Candidal infections are treated with fluconazole (Diflucan) or itraconazole (Sporanox). Griseofulvin is no longer considered effective therapy because of its long treatment course and poor cure rate. Response to oral antifungal agents in treating infections of the toenails is poor at best. Frequently, when the treatment stops, the infection returns.
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