Fungus (complete) Flashcards
Describe the characteristics of fungi with respect to morphology, cell composition, and biochemical functioning
- Heterotrophic – no chlorophyll
- Size: ranges from 3micro to several hundred ft
- Reproduction: sexual and asexual, unicellular and multicellular
- Rigid walls: chitin!!
- Sterol cell membrane: ergosterol
- Polysacch capcule in some
Explain why fungi differ from bacteria, plants, and animals
- Ergosterol! very specific to fungi
Not cholesterol :DDD
Explain the differences between yeast and hyphal forms of fungi (molds) and recognize that some organisms may be dimorphic
Y:
- unicellular
- asexual reproduction (fission, budding)
- shape varies (round, oval)
- colonies often creamy, pasty
- can form pseudohyphae
H:
- Tubular filaments
- Multicellular
- Form a mycelial mat! Elongation
- Typically branching
Describe how direct examination is used to diagnose fungal infections
- look under microscope
- scrap skin and add to slide w/ the following agents
KOH
Chlorazol black stain
India ink
Wood’s light
Describe how cultures are used to diagnose fungal infections
- What is the grow medium?
- What are the characteristics? (surface, edges, radial grooves, color of colony, color of converse/reverse)
- Lactophenol cotton blue examination
Describe how tissue is used to diagnose fungal infections
- Some fungus grows directly in tissue
- Some can only grow on the culture
What are other advanced techniques that may be used for certain infections or in specific circumstances?
- Serological
- PCR
Describe the mechanism of action of polyenes
“polyenes punch holes in cell membrane”
Describe the selective inhibition associated with polyenes
Bind to and inhibit ergosterol assembly
Won’t attack human cells!!
What is an example of polyenes?
Amphotericin
Describe the mechanism of action of azoles/triazoles
Interfere w/ ergosterol synthesis via 14-demethylase pathway
Describe the selective inhibition of azoles/triazoles
Focuses on esgosterol synthesis pathways (not in humans)
What is an example of azoles/triazoles?
Efinaconazole, luliconazole
Describe the mechanism of action of allylamines/benzylamines
- Fungacidal drug
- Inhibits squalene epoxidase => blocks ergosterol synthesis
- Squalene just accumulates => fungal cell death
Describe the selective inhibition of allylamines/benzylamines
Focuses on ergosterol synthesis (at an early point in synthesis)
What is dimorphism?
- Specific fungi may grow in 2 different forms
- Depends on environmental stimulus (often temperature)
What are examples of classic thermal dimorphic fungi?
Some Can Have Both Phases
1) Sporothrix schenckii
2) Coccidioides immitis
3) Histoplasma capsulatum
4) Blastomyces dermatitidis
5) Paracoccidioides basiliensis
Describe the morphology of Conidium
- An asexual spore
- come off aerial hyphae (can be macro or micro)
Describe the morphology of Sporangium
- An asexual spore
- have membranous sac
- looks like a lollipop
Describe the morphology of Chlamydospores
- An asexual spore
- fungi version of bacterial spores (protect its genetic material for a long time)
- resistant to adverse enviro conditions when its under stress
- don’t stick out — fluid as either terminal or intercalary
Describe the morphology of Arthrospores
- An asexual spore
- like a spine/vertebrae
- grow in culture
Describe the morphology of Spherules
- An asexual spore
- grow in tissue
- filled w/ small endospores
Describe the morphology of Blastoconidia
- An asexual spore
- small buds seen in yeast
- divide asymmetrically
