FUNGI AND OTHER ORGANISMS (HUMAN)

MYCOLOGY (MIC 206)

PARASITIC FUNGI AND HUMAN

Mycoses: Any fungal disease. Tend to be chronic because fungi grow slowly. Mycoses are classified into the following categories (based on the level of penetration into the body tissues): 1) Systemic or deep mycoses, often fatal.2) Cutaneous mycoses or dermatomycoses.3) Subcutaneous mycoses. 4) Superficial mycoses.5) Dimorphic systemic mycoses.

SYSTEMIC MYCOSES

Fungal infections deep within the body. Can affect a number if tissues and organs.

Usually caused by fungi that live in the soil and are inhaled.

Examples:Histoplasmosis (Histoplasma capsulatum): Initial infection in lungs. Later spreads through blood to most organs.Coccidiomycosis (Coccidioides immites): Resembles tuberculosis.

Systemic mycoses

Systemic Mycosis: Histoplasmosis

Disseminated Histoplasma capsulatum, lung infection.Source: Microbiology Perspectives, 1999.

CUTANEOUSMYCOSES

Cutaneous mycoses: Fungal infections of the skin, hair, and nails.

Secrete keratinase, an enzyme that degrades keratin. Infection is transmitted by direct contact or contact

with infected hair (hair salon) or cells (nail files, shower floors).

Examples: Ringworm (Tinea capitis and T. corporis) Athlete’s foot (Tinea pedis) Jock itch (Tinea cruris)

Cutaneous mycoses

Tinea pedis (feet)

Cutaneous Mycosis

Ringworm skin infection: Tinea corporisSource: Microbiology Perspectives, 1999

Candida albicans infection of the nails.Source: Microbiology Perspectives, 1999.

SUBCUTANEOUS

MYCOSES

Subcutaneous mycoses: Fungal infections beneath the skin.

Caused by saprophytic fungi that live in soil or on vegetation.

Infection occurs by implantation of spores or mycelial fragments into a skin wound.

Can spread to lymph vessels.

Subcutaneous mycoses

Superficial mycosesSuperficial mycoses: Infections of hair shafts and superficial epidermal cells. Prevalent in tropical climates.

3 Genera of dermatophytes:Trichophyton (Hair, Skin, Nails)Microsporum (Skin, Hair)Epidermophyton (Skin, Nails)

Tinea capitis (scalp)

Epidermophyton floccosum

Bifurcated hyphae with multiple, smooth, club shaped macroconidia (2-4 cells)

Dermatophyte Culture

OPPORTUNISTIC

MYCOSES

Caused by organisms that are generally harmless unless individual has weakened defenses:

AIDS and cancer patients Individuals treated with broad spectrum antibiotics Very old or very young individuals (newborns).

Examples:Aspergillosis: Inhalation of Aspergillus spores.Yeast Infections or Candidiasis: Caused mainly by Candida albicans. Part of normal mouth, esophagus, and vaginal flora.

Opportunistic mycoses

DIMORPHIC SYSTEMICMYCOSES

Caused by dimorphic fungal pathogens (by changing their morphological form.Geographically restricted and the primary sites of infection is usually pulmonary, inhalation of conidia.

Histoplasmosis:World-wide, espceially USA, sporadic cases do occur in Australia. Agent: Histoplasma capsulatum.

CoccidioidomycosisRespiratory infections: Endemic in south-western USA, nothern mexico and various centres in South America.Agent: Coccidioides immitis.

Dimorphic Systemic Mycoses