Mycology Flashcards
What do anti-fungal drugs target?
Ergosterol synthesis pathway and beta (1,3) glucan synthase
Fungal cell characteristics
Eukaryotes
Cell wall has glucan and chitin
Cell membrane contains sterols with phospholipid bilayer
___________ is the study of fungi
Mycology
Who is susceptible to mycoses
Critically ill and immunosuppressed patients with central vasc. catheters
Characteristics of fungi of clinical importance
Hyphae or pseudohyphae (septate, aseptate/ coenocytic, smooth, rough, branched)
Yeast (budding)
Conidia (macro or micro)
What does fungi grow as in the lab?
Mold or yeast on Sabouraud’s Dextrose Agar (SDA)
Dermal, SubQ species of pathogenic fungi
Microsporum species (M. canis)
Trichophyton (T. verrucosum)
Malassezia pachydermatis
Sporothrix schenkii (SQ)
Systemic species of pathogenic fungi
Histoplasma capsulatum
Blastomyces dermatitidis
Coccidiodes immitis
Cryptococcus neoformans (mold, monomorphic, opportunistic)
Opportunistic species of pathogenic fungi
Aspergillus fumigatus (mold, monomorphic, opportunistic)
Candida albicans and C. auris
Zygomycetes
Mucor, absidia, mortierella, rhizopus species
Multiple forms, opportunistic, specific situations, not common
________ is not a true fungus, but a fungus-like
Pythium insidiosum
Dermatomycoses
Ringworm
Trichophyton (verrucosum- cattle, rubrum- human, mentagrophytes- horse)
Microsporum (canis and equinum)
Non-dermatophytes
Malassezia pachydermatis and M. nana
Dermatophytes lab growth conditions
Dermatophyte test medium (DTM)
SDA agar
T. verrucosum @ 37C
Dermatophytes dx
Wood’s lamp (M. canis)- fluorescence
Hair/ skin microscopy
Culutre and ID (conidia)
KOH mount (ectotrix formation, arthropsores)
Malassezia and otitis/ dermatitis characteristics
Oval to cylindrical yeast
Normal flora in ear canal
Opportunistic and peanut shaped
Malassezia host related factors
Excess wax, high humidity, hairy, pendulous ears, dermatitis, etc.
The CS show by Malassezia is …
Lichenified skin (elephant skin)
Sporotrichiosis
“Rose-gardener disease”
Cause by S. schekii (dimorphic, SQ invasive mycosis)
North and South America
S. schenkii colony growth
Small white with no cottony aerial hyphae → becomes moist, wrinkled, leathery and darkens to brown or black
S. schenkii in culture/ extracellular
Septate, thin, branching hyphae, slender tapering conidiophores (mold)
Conidia: pear shaped rosette cluster
S. schenkii in tissue
Round oval fusiform budding (cigar bodies) - yeast
Histoplasma, Blastomyces, Coccidiodes characteristics
Thermally dimorphic
Inhalation
Many organ systems: mucocutaenous ulcers draining tracts + interal organs
Histoplasma
H. capsulatum capsulatum in N. America
Only intracellular localization fungus in host macros
Histoplasmosis distribution
Ohion and Mississippi river valleys (TN, MS, OH, MO, St. Lawrence river basins)
Histoplasmosis transmission
Humid environments with nitrogenous soils contaminated with bird or bat droppings (chicken coops, shed feathers, starling roosts)
Blastomycosis
B. dermatitidis
Yeast form: broad based budding
Lungs and associated LNs
Blastomycoses distribution
Upper mid-western and souther US along St. Lawrence river
Blastomycosis CS
No asymptomatic colonization
Hematogenous to skin, bones, UT, CNS
Cornea, retinal detachment and glaucomatous
Untreated blastomycosis is __________
FATAL (80%)
Coccidioides
Valley fever, CA fever, San Joaquin Valley fever, desert rheaumatism causes by C. immitis
C. immitis growth
25C and37C filamentous
38-40C spherule/ tissue form
Athrospores formed in 1-2 weeks
Coccidioides CS
In tissue or body fluids: large, round, thick walled spherules with endospores
Coccidiodomycosis (Valley Fever)
Desert/ semi arid areas of SW US and northern Mexico, Central and S. America
Lab Dx for Histoplasma, Blastomyces, Coccidiodes
Direct exam
Latex agglutination test
Immunofluorescence
Serology (Agar gel immunodiffusion)
What other fungal organisms can be found with AGID
Aspergillus, candida, paracoccidioides, farmers lung (hypersensitivity pneumonitis)
Crytococcal Ag lateral flow assay
Immunochromatographic test system for detection of capsular polysacc, Ags in serum and CSF
Cryptococcosis
Encapsulated yeast
C. neofromans
Found in soil, esp. with pigeon guano
Inhalation from environment
Cryptococcosis CS
Self-limiting lung infection
Pulmonary: pneumonia, dry cough, dyspnoea
Entrapulmonary: meningitis, skin lesions
Aspergillus growth
Colonies are white → yellow, green, brown, black
Velvety or cottony texture
Aspergillus physical characteristics
Septate hyphae, unbranched conidiophore (foot cells), vescicles
Chains of round conidia
Aspergillosis
Ubiquitous molds grown in decating debris (A. fumingatus)
Inhalation
Aspergillosis pathogensis
Spores colonize airway (asymptomatic) → local inflammatory response → lethal invasive infection
Candida
Yeast, opportunistic
Normal inhabitant of the the upper GI tract and moist skin folds
Candidiasis importance
Most common blood isolate
Grows in body yeast as pseudophyphae
C. albicans most common
Candida auris
Drug-resistant, spreads in healthcare facilities (anti-fungals don’t work!!)
Pythiosis (Swamp cancer)
FL horse leeches, Canckers, Ferida da Moda…
Caused by Phythium insidiosum
GIT and cutaneous forms
Pythiosis distribution
Wetland regions: gulf coast and south eastern states
Pythiosis CS
Motile endospores that affect lower extremities (skin) and ingested with contaminated water
Granulomatous ulcerative disease
___________ is causes by Pseudogymnoaocus destructans
White-nose syndrome
worst wildlife diseases, killed millions of bats
Zygomycosis
Commonly abundant saprophytic zygomycetes Mortierella, Absidia, mucor and Rhizopus
Aseptate, hyphae, grow rapidly
Zygomycosis in domestic animals
Gastritis and abortion in bovines
Mycotic abortion and placentitis (ruminants)
Guttural pouch and cervico-uterine infection (horses)
Cutaneous disease, mastitis, pneumonia
Zygomycosis dissemination
Fatal because of angio-invasion and thrombosis
Zygomycosis in humans
Diabetes is a high-risk predisposing factor
Polyene drugs
Amphotericin B, nyastatin
Ergosterol is the target
Imidiazole drugs
-azole group
Ketaoconazole, fluconazole, itraconazole
Ergosterol synthesis is the target
5-fluorocytocine
DNA synthesis inhibitor
Griseofulvin
Binds tubulin
Interference with fungal cells mitosis and concdentrated in the epithelium
Teratogenic
Terbinafine
Ergosterfol synthesis inhibitor
