Fungal Infections

Fungal infections (mycoses) of the skin, nails and hair are mostly caused by dermatophytes, yeasts or moulds. In the case of superficial skin mycoses, dermatophytes are found in about 80 % of cases, yeasts in about 10 – 15 % and moulds in 5 – 10 %. The most common systemic mycoses (fungal infections that affect the internal organs) in Central Europe are systemic candidosis, cryptococcosis and aspergillosis, and, more rarely, coccidioidomycosis and histoplasmosis. Blastomycosis predominantly occurs in North America, paracoccidioidomycosis and disseminated coccidioidomycosis mostly in Central and South America, and lobomycosis in South America.

In the following article, we will only look at fungal infections of the skin’s surface, the nails and the hair.

The dermatophytes include the species Trichophyton, Microsporum and Epidermophyton. The most common dermatophyte pathogen is Trichophyton rubrum. As dermatophytes need horny substance (keratin) for their metabolism, they only infect the skin’s surface, the nails and hair. Yeast infections are mostly caused by various kinds of candida, above all candida albicans. Yeast colonise the moist areas of the skin, such as those covered by nappies (diapers), the major body folds, the mucous membranes of the mouth and genitals and, in people whose immune system is weakened, also the internal organs. As far as moulds are concerned, only Scopulariopsis brevicaulis need be mentioned as causing fungal infections of the nails in Europe. To identify the pathogen, small scales of skin from the edge of the infected area or hair or nail clippings or scrapings are taken, which are examined under the microscope (native preparation) or transferred to culture dishes, where they can grow on a special culture medium. Because of the different speed of growth of culture preparations, a result can only be expected for dermatophytes after 2 weeks, for yeast fungi after 3 – 4 days and for moulds after about 1 week. However, the rate of growth for moulds can vary between 1 day and 3 weeks.

Note: Dermatophyte infections that are transmitted from animals (cattle, dogs, cats, etc.) usually cause more severe infections of the skin and hair, and are also more difficult to treat.

The clinical picture of a dermatophyte infection usually consists of a round or irregular shaped area of skin which is slightly scaly, is paler in the centre and has a raised edge. Small pustules (pimples) may also occur. The areas most frequently affected are the trunk, the scalp, the area of the beard in men, the feet, the groin (in men more often than in women) and the toe nails. Infections of the finger nails tend to be rare.

Fungal infections of the feet are one of the most common dermatological conditions. The incidence in Germany is estimated at 15 – 30 %. The infection is fostered by wearing enclosed shoes, including sport shoes (“athlete´s foot”), because of the warm, moist microclimate they produce. Mycoses of the foot usually start between the two outer toes, because in this area moisture is usually prevented from evaporating because of the inability to spread these two toes. Infections of the scalp and beard usually start with spots and pustules around the hairs. The fungus penetrates deep into the hair follicles, causing nodulation accompanied by severe inflammation. The condition can be aggravated by additional bacterial infection (superinfection), which frequently results in abscesses. It is vital to begin treatment as soon as possible in order to prevent destruction of the hair roots and the formation of scar tissue.

Onychomykose

Onychomykose

In the case of fungal infection of the nails, the toe nails are much more frequently affected than the finger nails. The nails first take on a white discoloration, subsequently changing to a yellowish-brown, and become thickened. Through bacterial superinfection (especially with pseudomonas aeruginosa), brown to greenish discoloration can occur. In the severer forms of nail thickening resulting from fungal infection, the nails also crumble (onychodystrophy). The most frequent causes are the dermatophytes Trichophyton rubrum, followed by Trichophyton mentagrophytes, and in the case of moulds, Scopulariopsis brevicaulis.

Yeasts tend not to infect the nails directly, but mostly cause inflammation of the finger nail walls. The infection of the nails then mostly spreads from the nail walls, as a secondary infection. The clinical symptoms are redness and swelling of the nail walls. The most frequent pathogens are Candida albicans, Candida parapsillosis and Candida tropicalis.

Predisposing factors for fungal infections of the nails (onychomycosis) are moist feet, vascular conditions with reduced blood circulation, diseases of the nerves, metabolism disorders such as diabetes mellitus, or immunological disturbances, in which the body’s resistance to illnesses is reduced.

A special form of candidosis is “nappie dermatitis“. The term “nappie dermatitis” is used for all inflammations of the nappy (diaper) area in babies, without specific identification of the cause. Most frequently, however, candida infections are found. The clinical symptoms are intense redness of the skin, scaling round the edges, and sometimes small pustules. The oral cavity is often also infected, and in nearly all cases the intestines.

Another highly problematic infection is candidosis of the genitals. In the case of women, the labia and vagina are frequently infected, and in men the glans penis and the inside of the foreskin. The most common cause of infection is Candida albicans, and less frequently also Candida glabrata, Candida krusei and Candida tropicalis. Predisposing factors are the use of the contraceptive pill, antibiotics, pregnancy, diabetes mellitus and immunological disturbances. The clinical symptoms are usually diffuse redness and swelling of the labia and vagina, accompanied by itching, smarting and a whitish discharge; there may also be a whitish film (fungal lawn). A common initial symptom is pain during sexual intercourse. In men, the symptoms are redness of the glans penis and the inside of the foreskin, small nodules and pustules, accompanied by itching and smarting. Predisposing factors in men are phimosis (tightness of the foreskin) and diabetes mellitus.

Candidosis of the mouth

Candidosis of the mouth | Foto: Enigma51, Lizenz: Creative Commons by-sa 3.0 / Kurz

Candidosis of the mouth causes a white or brownish coating, which is difficult to wipe or scrape off, in the area of the lips, tongue and mucuous membranes. Dryness of the mouth and smarting may also occur. In the case of people with dentures, candida infections often occur at the points of contact between the gums and the dental palate.

Note: The yeast Candida is part of the normal fauna and flora of the mucous membranes of the mouth and gastrointestinal tract. Treatment is only necessary if skin infections spread from these colonies or if people are affected whose immune resistance is reduced or severely impaired. Of itself, candida found in the oral cavity or intestine does not require therapy unless accompanied by other clinical changes!

For the external therapy of fungal infections by dermatophytes, yeasts and moulds, the following antimyotics are used (customary / generic name):

  • Imidazole: bifonzazole – clotrimazole – croconalzole – econazole – fenticonazole – isoconazole – oxiconizole – sertaconazole – tioconazole – miconazole
  • Allylamine: naftifine – terbinafine
  • Thiocarbamate: tolciclate – tolonaftate
  • Substituted pyridone: cyclopirox
  • Morpholine: amorolfine

For the treatment of yeast infections, specific local antimyotics are available such as nystatin, amphotericin B or natamycin. External antimyotics should be applied to an area of 2 – 3 cm beyond the visibly infected area, and should continue to be used for at least 1 week after the visible systems have disappeared. Local application should be done twice a day.

These products are available in the form of powders, creams, ointments and lotions.

Fungal infections of the hair and nails usually require treatment with internal antimyotics, e.g. griseofulvin, fluconazole, itraconazole, ketoconazole or terbinafine. Griseofulvin is effective against dermatophytes and fluconazole against yeast fungi. Itraconazole is highly effective against dermatophytes, yeasts and moulds. The same spectrum of activity (exception: Microsporum) is provided by ketoconazole. Terbinafine is excellent for treating dermatophytes, but also yeasts and moulds. These systemic antimyotics are taken in tablet form.

For the therapy of Candida infections of the mucous membranes of the mouth and the gastrointestinal tract, nystatin, amphotericin B or natamycin can be taken in the form of pastilles, suspensions and tablets. Also miconazole in gel form is used against yeast infections of the mouth. The gels and suspensions are used for treating the mouth, gullet and stomach, the tablets for the intestine.

Because of the specificity of the pathogen, nystatin, amphotericin B and natamycin in the form of pastes, creams and ointments should be used for the local treatment of yeast infections.

Note: In the case of yeast infections of the genitals, it is essential for the other partner to be treated at the same time in order to avoid the “ping-pong” effect (i.e. re-infection of the treated partner by the untreated partner).

Besides their broad range of effectiveness against dermatophytes, yeasts and moulds, another advantage of the imidazoles and substituted pyridones is their high efficacy against gram-positive bacteria. These local antimyotics are also available in powder form in order to “dry out” moisture in the body folds and between the toes.

In the case of nail fungus infections (onychomycosis) of the visible outer part of the nail, local treatment with products containing 1 % bifonazole and 40 % urea results in removal of the infected body of the nail. When the infected nail has been removed, therapy continues with bifonazole in the form of a lotion or cream. Another effective treatment for onychomycosis is antimycotic nail varnish containing amorolfine or ciclopirox. Treatment has to be carried out twice a week over a period of 6 – 12 months.

Note: Growth of the finger nails from the matrix to the tip takes about 6 months, that of the toe nails about 12 – 15 months. This is the reason for the different duration of treatment for mycosis of the finger nails and the toe nails.

For infection of the nail matrix, i.e. the part of the nail covered by the nail wall, internal treatment with griseofulvin, itraconazole or terbinafine is necessary.

Pityriasis versicolor is a chronic, superficial, non-inflammatory fungal infection of the skin. It is caused by Malassezia furfur or the hypha fungi Pityrosporum ovale or Pityrosporum orbiculare. This lipophile yeast only occurs in the keratin of the outer skin in people over the age of about 15, because only from this age on are the sebaceous glands sufficiently active to produce sebum in the required quantities which this pathogen needs for its metabolism.

The clinical symptoms are sharply delineated, scaly brownish areas on the trunk or, less frequently, on the neck, the upper arms or thighs. On exposure to sunlight, the areas become pale, causing white specks on an otherwise brown skin. Most patients only go to the doctor because of these white spots.

Predisposing factors for Pityriasis versicolor are high levels of moisture on the skin, especially in heavy sweating during the summer time or in subtropical and tropical regions. In moderate climate zones, this skin condition is observed in only about 2 % of the population, but in subtropical and tropical zones in up to 40 % of the population.

Local treatment can be undertaken with selenium disulphide lotion or shampoo, salicyclic acid spirit, or the imidazoles (bifonazole, clotrimazole, econazole, itraconazole, miconazole, fenticonazole, sertaconazole, tioconazole, isoconazole and oxiconazole) in cream or lotion form. Econazole is also available as a shower gel. In cases of resistance to external treatment, fluconazole, itraconazole or ketoconazole is administered internally.skinpilot side tour