Principles of Epidemiology and Microbiology
Lesson 2: Public Health Microbiology
Section IV: Fungi
2-20
2-20. PATHOGENIC FUNGI
a. Fungal infections are of two types: localized skin infections (dermatomycoses), and systemic infections. Although the former are far more common, the latter generally have more serious consequences. Table 2-6 lists the more common fungus diseases and the important etiological agents in each. Note that frequently more than one species of organism may cause identical symptoms.
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Disease |
Synonym or Brief Description
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Important Etiological Agents
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CUTANEOUS AND SUPERFICIAL MYCOSES
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Tinea capitis'
Tinea corporis
Tinia barbae
Tinea cruris
Tinea pedis
Tinea versicolor
Otomycosis (aspergillosis)
Cutaneous Candidiasis (moniliasis, thrush)
Mycetoma
Actinomycosis
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Ringworm of the scalp
Ringworm of the body
Infection of bearded area of face and neck
Ringworm of the groin (jock itch)
Ringworm of the feet (athlete's foot)
Depigmented, scaly patches of skin
Fungus infection of the ear canal
Yeast infection of nails, skin, mouth, Vagina
Tumor-like swelling, draining abscess
Chronic, suppurative or granu- lomatous disease of jaw, thorax, or abdomen
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Microsporum spp Trichophyton spp
Same as Tinea capitis
Trichophyton spp
Trichophyton spp Candida albicans Epidermophyton floccosum
Same as Tinea cruris
Malassezia furfur
Aspergillus spp
Candida albicans and otherspecies
Pseudallescheria boydii and other
Actinomyces israelii [actuallyclassified as bacteria, but cause fungus-like infections] |
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Table 2-6. Common fungus diseases. (continued)
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Disease |
Synonym or Brief Description
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Important Etiological Agents
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SUBCUTANEOUS AND SYSTEMIC FUNGUS INFECTIONS
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Nocardiosis
Chromoblastomycosis
Sporotrichosis
Blastomycosis
Coccidioidomycosis
Histoplasmosis
Cryptococcosis |
Infection of lungs, other organs, and lower extremities (Madura foot)
Warty nodules or vegetations of skin and subcutaneous tissues
Ulcers of skin and underlying tissues and gumma-like swelling of regional lymph nodes.
Inflamatory lesions of the skin, lungs, or bones.
Self-limited respiratory disease or chronic progresssive infection of various organs
Fungus infection of the lungs, with fever; anemia; loss of weight, enlargement of lymph nodes, liver, spleen
Systemic fungus infection of lungs or meninges
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NocardIa asteroids [actuallyclassified as bacteria, but cause fungus-like infections] N. brasIlIensIs
Cladosporium carrionii Fonsecaea pedrosoi
Phialophora verrucosa Sporot schenkii
Blastomyces dermatltidis
Coccidioides immitis
Histoplasma capsulatum
Cryptococcus noeformans |
Table 2-6. Common fungus diseases (concluded)
b. Diseases caused by fungi are collectively called mycoses (singular, mycosis). They are divided into four general categories on the basis of the primary tissue affected by the pathogen:
(1) Superficial mycoses are infections limited to the hair and dead layers of the skin.
(2) Cutaneous mycoses (dermatophytoses or ringworm) affect only the skin, hair, and nails.
(3) Subcutaneous mycoses affect the subcutaneous tissue below the skin and occasionally bone.
(4) Systemic ("deep") mycoses infect the internal organs and may spread throughout the host
c. Those fungi infecting the outer layers of the skin are rarely severe and are usually transmitted by contact with infected animals or humans. The agents of subcutaneous and systemic mycoses, however, are normally saprophytic fungi growing in the soil. Humans generally acquire these mycoses only when the spores of these organisms are either inhaled or introduced into the body through a break in the skin.
d. Some fungi incapable of causing infectious diseases produce toxic substances that poison the person who ingests them. These substances are collectively called mycotoxins. The most commonly known mycotoxin poisoning is from certain mushrooms; however, mycotoxins may be produced by fungi growing on grain, nuts, and other agricultural products.
