Groups of Mycoses (With Diagram)

The following points highlight the top two groups of Mycoses (Diseases caused by Fungi). The groups are: 1. Cutaneous Mycoses 2. Systemic Mycoses.

Group # 1. Cutaneous Mycoses:

Fungi penetrate the skin, hair and nails and grow as branching filaments or hyphae. Only the dead outer layer of these tissues is invaded; whereas the deeper or living layers cannot support the growth of hyphae. In skin infection, the metabolites of the fungi diffuse into deeper living skin cells.

People infected with these fungi become sensitive to these substances, as a result there is skin response with reddened erythematous areas and itching.

In the erythematous area, soon appear the little blister. The centre of the lesion becomes scaly and heal, it is then surrounded by an enlarging red outer ring covered with blister. These conditions are known as “ringworm“.

In hair infection, the shaft of the hair which is just formed above the living cells in the hair follicles, is attacked by superficial fungi (dermatophytes). As the living cells continue to form the hair shaft, the infected portion of the shaft is brought upward.

The penetration of hyphae of some fungi in the internal structure of the hair shaft may result in easily breakage of the hair within the hair follicle. In this condition, the infected area of the scalp appears bald.

In cases where the surface of the hair shaft is only infected by the hyphae of the fungi, the hair breaks often and thereby, the scalp appears as moth-eaten. The fungal infection of the hair of children is very common, compared to adults. Infective nails become yellow, black and brittle.

Tinea (Ringworm):

The medical term “tinea” implies the superficial fungal infection (ringworm) of the skin, hair and nails. Tinea capitis is the fungal infection of the hair of the scalp. When the foot is infected, the condition is called “athlete’s foot” or tinea pedis. Fungal infections of the nail and groin are named, respectively, as tinea unguium and tinea cruris.

Dermatophytes (derm, skin; phyte, plant) are fungi which are infectious. They are groups of related fungi which embraces three genera and 20 species. Species of fungi occurring in the skin, hair and nail of man and animals are fully responsible for the direct infection from one individual to another and their hyphae in the tissues may directly develop into chains of spores after a long time.

Other types of the dermatophytes may live in soil; when they are rubbed on to the skin, they may cause the infection. The infections caused by dermatophytes are collectively called dermatophytoses or dermatomycosis.

Dermatophytes and their Location of the Infections:

1. Hair, skin, rarely nails:

Microsporum canis ( ringworm, tinea capitis in children)

M. audouinii ( epidemic tinea capitis in children).

M. gypseum (ringworm, tinea capitis).

2. Skin, hair and nails:

Trichophyton mentagrophytes (athlete’s foot, infection of nails and skin).

T. rubrum (athlete’s foot, tinea cruris, nail infection, sycosis).

T. tonsurans (tinea capitis),

T. schoenleinii (favus)

3. Skin, nails, not hair:

Epidermophyton floccosum (athlete’s foot, tinea cruris, nail infection),

* Sycosis – pustular inflammation of the hair follicle of the face due to dermatophytes (barber’s itch).

* Favus-dermatomycosis of the scalp characterised by honeycomb like, itching yellow crusts over the hair follicles.

Application to Nursing:

The nurse should have the knowledge that the hyphae and spores of fungi can initiate the infection, if they are lodged on the skin or scalp or another susceptible individuals. Therefore she should take precautions to dispose off scale and stub of infected hair. She should also remember that the infected child can transmit his infection to his school­mates and even to his pet animal.

Dogs and animals should be carefully examined for scaly patches with loss of hair as they may become the source of infection to other human beings. Thus the owners of these animals should be advised to get these animals treated; if not responding to the treatment, they should be discarded.

Group # 2. Systemic Mycoses:

The systemic mycoses are caused by fungi which occur in soil as saprophytes.

The dust containing spores and hyphae inhaled by man may get logged in the lung, they grow; if they overcome the host defense mechanism, they multiply and produce lesions in the lung; and from these lesions they may be carried through the blood stream to various parts of the body where they setup the infection and lesions are produced.

The lesion is limited to a small area of the lung in some people and may heal soon. Wounds of hands and feet are the portals of entry for soil fungi. Only few pathogenic fungi develop the infection.

Coccidioidomycosis:

The causative agent, Coccidioides immitis, of the disease is commonly encountered in the soil of United States and grows as mould in soil. It is a diphasic fungus because it forms spherule in the tissue. Most of the people are infected by inhalation of dust laden with fungus; they show only a mild influenza like syndrome with fever.

Erythema nodosum painful red lumps appear on the legs of few patients. Pulmonary symptoms are very severe in some cases resembling to pneumonia and in others they may be suggestive of tuberculosis.

If localised, giant cavities are formed in the lung. If the fungus is disseminated to various parts of the body, skin, bone marrow lesions may develop; meningitis is common and the patient will become seriously ill. In addition to the cultivation of the fungus. Skin test, Coccidioidin similar to tuberculin test is an useful test for diagnosis (Fig 91.2).

Histoplasmosis:

Histoplasma capsulatum (diphasic fungus) causes histoplasmosis and grows commonly in the soil of United States. The human infection occurs through inhalation of its spore. Some infected people experience symptoms like influenza or pneumonia or tuberculosis. The prognosis is grave if the pulmonary disease is severe. If the liver or spleen is affected through dissemination the patients are seriously ill.

Skin test with histoplasmin and X-rays can be used for the diagnosis. Blastomycosis, reported in United States of America and Canada, is caused by Blastomyces dermatitidis, diphasic fungus. Lung infections begin with the inhalation of spore or hyphae. Dissemination may be to all parts of the body. Lesions on the skin and in the bones are especially common. Skin test with Blastomycosin can be carried out.

Opportunistic Mycoses:

They are caused by a large number of soil fungi that are capable of producing infection in man under unusual conditions.

Candiasis:

It is caused by Candida albicans which is yeast like organism commonly found in the mouth and the genital tract of healthy people, but under favourable conditions they multiply heavily, invade the tissues, and grow into long filaments and in the form of budding yeast like cells.

Diabetes, debility, steroid therapy and prolonged administration of antibiotics are the factors which promote the growth of C. albicans. Candida vaginitis may occur in pregnant women. If the hands are wet for longer period, some people may develop skin lesions of the inter-digital webs or of the finger nail.

Though:

Though C. albicans (oral thrush) is normal flora of the mouth and genital tract, it may invade tissues, may set-up the inflammation and produce pseudo membrane on the lip and the mouth. This condition is called “Thrush“. It is also common in neonates who acquire this infection from the infected mothers while passing through the birth canal.

Ordinarily the bacteria of the genital tract suppress the growth of C. albicans, but if the patients are under antibiotic therapy for a longer period, the antibiotics may inhibit the growth of bacteria. As a result, C. albicans is free from the bacteria. Itching or perianal rash may also occur.

Besides, if the lung tissue is damaged by tuberculosis or cancer or other diseases, C. albicans may multiply in the dead tissue and aggravate the infection. C. albicans rarely enter the blood stream; if it invades at all, it may be cause of vegetation of heart valves or lesions in the kidney.

Treatment:

Nystatin is the drug of choice for candidiasis. Griseofulvin (oral administration). Betrafen cream and Zole powder (local application) for 21 days are very effective for superficial mycoses.

Application to Nursing:

In systemic mycoses, the nurse should take care to dispose off the sputum, pus, dressing and other materials containing the fungus. Otherwise there is every possibility for the spread of the infection to the newly born infants from the mother. C. albicans vaginitis should be properly treated.