Fungi Flashcards
Basic character of fungi
Mold or yeast forms
Cell type of fungi
Eukaryotic with outer wall and cell membrane
Classification of fungi
spores; typical disease caused
Cell wall of fungi
Rigid composed of chitin and glucan
Cell/particle membrane of fungi
Cell membrane has ergosterol instead of cholesterol
Reproduction of fungi
Sexual and/or asexual; spores; yeast budding
Coencytic hyphae
Hyphae with no septa
Septate hyphae
Hyphae with septa
Mycelium
Vegetative part of a fungus that is network of hyphae (mold)
Fruiting bodies
Macroconidia (with released conidia spores)
Endospores (conidia enclosed in a sporangium sac)
Yeasts fungal growth and morphology
Unicellular; reproduce - asexually by budding (blastoconidia) or sexually by fusion; growth on solid culture plates resembles bacterial colonies; most fungal pathogens can grow as yeast in the body
Molds fungal growth and morphology
Multicellular, grow as long, tube-like extensions of the cell wall; hyphae
What infection is associated with mycelia?
Mycetoma infection - chronic infection of skin and subcutaneous tissue (causes masses underneath the skin)
Reproductive structures of mold
Asexual: conidia and arthroconidia
Sexual: ascospores and basidiospores
Conidia
Produced by budding
Arthroconidia
Hyphal segments fragment into individual cells
Ascospores
produced in ascus sac
Basidiospores
produced in basidium
Dimorphism
Ability of a fungus to grow as a yeast or a mold depending on environmental conditions; dimorphic pathogens generally grow as yeasts at body temp (37C), molds in their natural soil environment (25C)
Superficial mycoses
Colonize outermost layers (keratinized) of skin, nails, and hair
Malassezia furfur labs and morphology
Spaghetti and meatball organization; KOH, calcofluor, PAS, standard medium with olive oil (cream)
Pityriasis (tinea) versicolor
hypo/hyperpigmented, irregular, well-demarcated macules (can be raised or scaled); predisposing factors - folliculitis, dacryocystitis (infection of lacrimal sac)
Hortaea (exophiala) werneckii labs and morphology
Black fungus, dematiaceous, branched hyphae, arthroconidia and elongate budding cells; KOH, H&E, sabouraud dextrose agar media = black mold
Tinea nigra
Palms and soles; solitary, irregular pigmented macule, no scaling or invasion into hair follicles; asymptomatic
Malassazeia furfur clinical disease
Pitariasis (tinea) versicolor
Hortaea (exophiala) werneckii clinical disease
Tinea nigra
Hortaea (exophiala) werneckii epidemiology
- Less than 1% of fungal infections
- (Sub)tropical
- children and young adults
- trauma in dermis
- associated with water
Tricosporon spp. cause…
White piedra
Trichosporon spp. morphology and lab
- Hyaline septate hyphae
- Arthroconidia and some blastoconidia
- Standard medium - cream-colored colonies
Piedraia hortae causes…
Black piedra
Piedraia hortae morphology and lab
- Spindle-shaped ascospores within asci
- Branched, pigmented hyphae
- standard medium - velvety
White piedra
- Groin, axillary, and less commonly scalp hair involved
- hair stem covered with white fungus
- no damage to hair shaft
Black piedra
Small, dark nodules on hair shaft (mostly involve the scalp)
Cutaneous mycoses clinical disease
Cause dermatophytosis (tinea, ringworm)
Symptomatic infections of cutaneous mycoses
Invasion of skin (corneum), hair, and nails (keratinized layers too)
Morphology of cutaneous mycoses
- Hyaline (translucent) septate hyphae
- Macroconidia vs micro help in identification
Hair infection where arthroconidia form on outside of hair
Ectothrix
Hair infection where arthroconidia form in inside of hair
Endothrix
Hair infection where hyphae, arthroconidia, form in empty spaces of hair (air bubble appearance)
Favic
Major symptoms of cutaneous mycoses
Itching
↑ inflammation – contracted from animals
↓ inflammation – contracted from human
Tricophyton spp. cause which diseases…
- Tinea pedis
- Tinea corporis
- Tinea cruris
- Tinea capitis
- Tinea barbae
- Tinea unguium
Epidermophyton floccosum cause which diseases…
- Tinea pedis
- Tinea cruris
- Tinea unguium
Microsporum spp. cause which diseases…
- Tinea corporis
- Tinea capitis
How can cutaneous mycoses be identified in general?
By microscopy (aided by KOH and stain)
Tinea corporis
Ringworm of trunk and legs
Tinea pedia
Athlete’s foot
Tinea capitis
Scalp, eyebrows, lashes ringworm
Tinea barbae
Ringworm of the beard
Tinea unguium
Onychomycosis (nail infection)
Fruiting bodies of microsporum canis
- Macroconidia
- rough-walled, spindle-shaped (ends pointed)
Fruiting bodies of trichophyton mentagrophytes
- Macroconidia
- short, thin-walled, cigar-shaped (ends rounded)
Fruiting bodies of trichophyton rubrum
- Macroconidia
- Long, narrow, thin-walled pencil shape
Fruiting bodies of epidermophyton floccosum
- Macroconidia
- Smooth-walled, club-shaped
Sporothrix schenckii morphology
- Ubiquitous in soil
- Dimorphic fungus
- Room temp – Mold
- 37°C – pleomorphic yeast
Sporothrix schenckii mold phase morphology
- Septate hyphae
- Oval conidia
- Conidiophore (stalk that carries conidia) rosette-shaped
Sporothrix schenckii yeast phase morphology
Cigar-shaped bud
Sporothrix schenckii epidemiology
- Japan, North America, and South America - warmer climates
- Most common in individuals who work outside (gardeners)
- trauma (finger prick, cut)
- Cats and armadillo – zoonotic transmission
Sporothrix schenckii disease
Sporotrichosis
Sporothrix schenckii labs
- Culture is gold standard (SDA) and associated morphology
- Appearance of Splendore-Hoeppli material in H&E (asteroid body)
Sporotrichosis
- Primary nodule site presents as small nodule that may ulcerate
- Secondary nodules present as a linear chain of painless subcutaneous nodules
- Spread along lymphatic drainage
- Nodules may ulcerate with pus discharge
Chromoblastomycosis epidemiology
- Rural areas of tropics
- Involves legs and arms
- In the Americas – F. pedrosoi – lower extremities
- In Australia – C. carrionii – upper extremities
Chromoblastomycosis biology and morphology of causative fungi
- All species are dematiaceous (pigmented) molds
- Morphologically diverse
- In tissue, all spp form muriform cells (sclerotic bodies)
- Chestnut brown due to melanin in cell wall
- Divide by internal septation – cells have vertical and horizontal lines
- Pigmented hyphae may be seen
Chromoblastomycosis
-Chronic infection of skin and subcutaneous tissue; pruritic
Indolent (slow) growing verrucous nodules/plaques
-Presentation indicates a well-established infection
-Early lesions:
-Small, warty papules that grow slowly
-Established infection:
-Multiple, large cauliflower-like growths
-Hyperkeratotic lesions and fibrosis
-Complications
-Squamous cell carcinoma
-Bacterial infection
Chromoblastomycosis labs
- Scrapings from lesions
- Microscopy (Muriform** cells)
- 20% KOH treatment
- Biopsy – H&E
- Cayenne pepper appearance of lesions**
- Fungal cultures
- Slow-growing colonies
- Dark pigments
- Velvety appearance
Mycetoma epidemiology
- Predominant in tropics with low rainfall
- Africa, India, Brazil, Middle East
- Usually enters body through traumatic implantation**
- Foot** most common location
Mycetoma general biology and morphology
- Result in granuloma formation that contain hyphae aggregates termed granules or grains**
- Dematiaceous (black grain) or hyaline (pale or white grain)
- Septate and branching hyphae** may be embedded in cement-like coating
- Splendore-Hoeppli material present
Mycetoma chronic disease
- Clinical Triad: tumor, sinus tracts, granules
- Early lesions:
- Small, painless, subcutaneous nodules/plaques
- Established infection:
- Granulomas enlarge and sinus tracts form on surface
- Serosanguineous fluid drainage (can send to lab)
- Muscle and bone destruction – deformations
Mycetoma complications
S. aureus infection
Mycetoma immune reaction
Pseudoepitheliomatous hyperplasia
- Hyperplasia (increased cell production) of the epidermis
- Chronic inflammation
- Generally benign
Mycetoma labs
- Scrapings from lesions
- Microscopy (septate, branching hyphae with large swollen cells on edge)
- 20% KOH treatment
- Gram stain to eliminate bacterial infection
- Microscopy (septate, branching hyphae with large swollen cells on edge)
- Histopathology
- H&E stain
- Fungal cultures
- RT and 37°C for six to eight weeks
Candida spp.
Opportunistic pathogen, yeast; normal commensal in human GI, vaginal tract, and skin
Candida transmission
- Endogenous – involves commensals on self
- Exogenous – hospital acquired
Candida morphology
- Oval yeast-like cells that produce buds (blastoconidia) and chlamydospores
- Produce pseudohyphae** and hyphae
- C. albicans forms germ-tubes**
Candida virulence factors and pathogenesis
- Adherence – Hyphal Wall Protein (attachment protein to epithelial cells)
- Proteinases – hydrolyze host proteins (collagen and fibronectin) that are involved with host protection
- Phospholipases – lecithinase that cleaves fatty acids from glycerol backbone of membrane phospholipids
- Phenotypic switching** – expression of cell wall glycoproteins, proteolytic enzyme secretion, decreased susceptibility to oxidative damage by neutrophils
Candida diseases
Cutaneous candidiasis, diaper dermatitis, paronychia**, perianal candidiasis, balanitis (balanoposthitis if prepuce), chronic mucocutaneous candidiasis
Cutaneous candidiasis
- Develops in folds of skin (intertrigo); armpits, groin, between fingers, and under the breasts
- Warm, moist environments
Diaper dermatitis
- Secondary infection after bacterial infection
- Beefy red plaques, satellite papules, and pustules
Paronychia
Nail-skin interface
Predisposing factors to candidiasis
- Immunosuppression (drug-induced, AIDS)
- Neutropenia (WBC < 500/mm3)**
- Burn victims
- Assisted ventilation, indwelling catheters
- Diabetics – high glucose impairs neutrophil function
- Broad-spectrum antibiotic use
Candida labs
KOH with calcofluor, PAS, GMS, Gram stain**
Cultures: smooth, white, creamy, domed colonies
Germ tube test:
-Cells incubated in serum for a few hours at 37C
-A slender structure protrudes out or cell (looks like a comma)
Tinea cruris
Jock itch
