Fungi Flashcards
(31 cards)
What is thermally dimorphic?
Different structures at different temperatures (usually mold in environment/room temp and yeast at body temperature)
Describe the cell wall structure of fungi
chitin in inner most layer, then glucan, then mannoproteins. does not contain peptidoglycan
also contains ergosterol
Why are fungal infections harder to treat in humans than bacterial infections?
Because they are eukaryotes and have many organelles, enzymes and processes similar to humans. Characteristics unique to fungi must be targeted for treatment.
Is transmission more environment to person or person to person for funal infections?
Environment to person: most fungi in water, soil or decaying vegetation
Which factors of human skin contribute to fungal infection resistance?
pH, fatty acid content, epithelial turnover, normal bacterial flora (inhibit space for growth of pathogen)
How can fungi colonize the skin?
o Direct inoculation
o Systemic infection –> seeds into skin
o Systemic infection–> immunologic reaction in skin
How is a KOH Preparation done? What is it used for?
o KOH prep is used to image and diagnose fungal infections (look for yeast or hyphae)
o First swab with 70% EtOH (alcohol), scrape surface to remove skin scales/hair with fungus, treat scraping with 10% KOH to destroy tissue, leaves the hyphae or yeast cells for imaging
What are the four kinds of fungi based on depth of infection in skin
superficial mycoses- ex: tinea nigra
cutaneous mycoses- dermatophytosis (skin, hair, nails)
subcutaneous- sporotrichosis
systemic- cocidiodomycosis
Malassezia furfur…
- pityriasis versicolor (lipophilic yeast-like organism with spaghetti appearance)
- common on upper torso/arms/abs,
- causes hyper or hypopigmented macular lesions
Hortaea werneckii causes…
- Tinea nigra (dimorphic)
- Produces melanin black or brown color
- Lesions on palms and soles
piedra hortae causes…
Black piedra
Hard nodules along hair shaft that contain the spores
Trichosporon beigelii causes…
White piedra
makes white sleeve around hair shaft on scalp, mustache and beard
tinea corporis
ring worm (cutaneous dermatophytosis)
tinea cruris
jock itch, ( cutaneous dermatophytosis)
tinea pedis
athletes foot (cutaneous dermatophytosis)
tinea manuum
palms of hand (cutaneous dermatophytosis)
tinea capitis
scalp infection (endothrix- hair breaks at scalp; exothrix- hair breaks above scalp)
tinea barbae
infection of beard hair
tinea ungium
infection of nail
Trichophyton rubrum, T. mentagrophytes are common fungi for…
cutaneous mycoses (dermatophytoses)
Sporothrix schenckii
subcutaneous infection, causes sporotrichosis, dimorphic, found in soil, creates small ulcer at implant site and spreads through lymphatics
Chromoblastomycoses
warty nodules at implant site, epithelial overgrowth, septate fugus producing a dark brown pigment
Describe characteristics and pathology of coccidiodoides immitis.
o Found in the soil, dimorphic (mold in environment, sphereule that makes endospores in body)
o Diseases- Valley Fever (pneumonia), can lead to meningitis
o Pathology-Fungi in soil, stirred up by environment or tractors etc, Aerosolized, breath it in, spherules produced which turn into endospores, can cause pneumonia in lungs, can go out of lungs and into CNS meningitis
o Diagnosis- history, positive skin test, serum antibody to c. immitis, positive culture
Describe characteristics and pathology of Histoplasma capsulatum
o Properties- found in soil with bird/bat droppings, dimorphic fungus, mold in soil and yeast in body yeast is phagocytosed by macrophages, common in Ohio and Mississippi Valleys (SE)
o Diseases- Cave disease, spelunker’s disease, pneumonia
o Pathology- similar to TB, respiratory transmission; Fungus in soil, exposed to bird/bat, fungus kicked up into air, inhaled by human, macrophage eats fungus and it spreads; might produce an active infection or be dormant
o Diagnosis- positive skin test similar to TB, biopsy, serology
