BS537: Mycosis

What are yeasts?

Single celled fungi that reproduce by budding

What are molds?

Multicellular fungi composed of hyphae

Are fungi prokaryotic or eukaryotic?

Eukaryotic microorganisms

What sterol is found in fungal cell membranes?

Ergosterol

Are fungi mostly aerobic or anaerobic?

Mostly aerobic

How do molds reproduce?

Sexually

How do yeasts reproduce?

Asexually by budding

Where are molds and yeasts commonly distributed?

Air, dust, fomites, and normal flora

Approximately how many fungal species are linked to disease in animals?

About 300 species

What are the four types of mycotic diseases?

Hypersensitivity, mycotoxicosis, mycetismus, and mycoses

What is mycotoxicosis?

Poisoning by food contaminated with toxin producing fungi

What is mycetismus?

Ingestion of preformed mushroom toxins

What are mycoses?

Fungal infections

What are superficial mycoses confined to?

Keratinized epidermis including skin, hair, and nails

What are dermatophytoses also called?

Ringworm or tinea

What genera commonly cause dermatophytoses?

Trichophyton, Microsporum, and Epidermophyton

What is the primary portal of entry for systemic mycoses?

Respiratory tract through inhaled spores

How are subcutaneous mycoses commonly acquired?

Traumatic inoculation into the skin

What are major fungal virulence factors?

Thermal dimorphism, toxin production, capsules, adhesion factors, hydrolytic enzymes, and inflammatory stimulants

What are important antifungal defenses?

Integrity of barriers, respiratory cilia, cell mediated immunity, phagocytosis, and inflammation

How are mycotic infections diagnosed?

Microscopy, culture, biochemical tests, and serological tests

What antifungal drugs are commonly used?

Amphotericin B, flucytosine, azoles, and nystatin

What are cutaneous mycoses?

Fungal infections confined to skin, hair, and nails

What conditions facilitate cutaneous mycoses?

Moist and chafed skin

What is tinea capitis?

Ringworm of the scalp

What is tinea barbae?

Ringworm of the beard

What is tinea corporis?

Ringworm of the body

What is tinea cruris?

Ringworm of the groin or jock itch

What is tinea pedis?

Ringworm of the foot or athlete's foot

What is tinea unguium?

Ringworm infection of the nails

How is tinea pedis commonly spread?

Exposure to contaminated public surfaces

What topical antifungals are used for dermatophytes?

Tolnaftate and miconazole

What oral antifungals may be used for dermatophytes?

Lamisil or griseofulvin

What causes tinea versicolor?

Malassezia furfur

What are the symptoms of tinea versicolor?

Mild chronic scaling and mottling of the skin

What is sporotrichosis also called?

Rose gardener disease

What organism causes sporotrichosis?

Sporothrix schenckii

Where is Sporothrix schenckii commonly found?

Soil, plant debris, thorns, moss, and timber

What is the incubation period for sporotrichosis?

2 to 12 weeks

What lesion develops in sporotrichosis?

Nontender erythematous papulonodular lesions

What is chromoblastomycosis?

A slowly developing fungal infection limited to skin and subcutaneous tissue

What type of lesions are seen in chromoblastomycosis?

Verrucous lesions

What are opportunistic fungal pathogens?

Fungi that cause disease mainly in immunocompromised hosts

What percentage of nosocomial infections are due to opportunistic fungi?

About 10 percent

What organism causes candidiasis?

Candida albicans

What type of organism is Candida albicans?

A widespread yeast

What structures can Candida albicans form?

Pseudohyphae and true hyphae

What is thrush?

A thick white adherent growth on the mucous membranes of the mouth and throat

What is vulvovaginal candidiasis?

Painful inflammatory yeast infection of the female genital tract with whitish discharge

Where does cutaneous candidiasis commonly occur?

Chronically moist skin areas and burn patients

What opportunistic infection is caused by Aspergillus fumigatus?

Aspergillosis

Who is at high risk for aspergillosis?

AIDS, leukemia, and transplant patients

Where does aspergillosis most commonly occur?

Lungs

What can invasive aspergillosis cause?

Necrotic pneumonia and infection of other organs

What organism causes PCP pneumonia?

Pneumocystis jiroveci

Who commonly develops Pneumocystis pneumonia?

AIDS patients

What does Pneumocystis pneumonia do in the lungs?

Forms secretions that block breathing

What are examples of systemic fungal pathogens?

Histoplasma capsulatum, Coccidioides immitis, and Blastomyces dermatitidis

What disease is caused by Histoplasma capsulatum?

Histoplasmosis

What is another name for histoplasmosis?

Ohio Valley fever

Where is Histoplasma capsulatum most prevalent in the United States?

Eastern and central regions

What type of soil favors Histoplasma growth?

Moist soil high in nitrogen

How is Histoplasma capsulatum transmitted?

Inhalation of conidia spores