Immunology Week 4 - Fungi 1 Flashcards
What is the mechanism of Azole?
interfere with ergosterol biosynthesis
What are fungi cell walls made of?
carbohydrate polymers, chitin, a-glucan, B-glucan, a-mannon and mannoproteins
What does coenocytic mean?
Multi-nuclei
What makes up a mycelium?
multiple hyphae
What is a hyphae?
branching cylindric tubules varying in diameter from 2-10 mM
What is Chlamydoconidia?
A type of spore: thick walled single cells that are resistant to adverse conditions
What is Arthroconidia?
A type of spore: single celled conidia that are formed by the disjoining of hypal cells
What is Conidiospores? What are the two types?
A type of spore: medically important - borne naked on specialized structures
Two types:
macroconidia - large, multicelled conidia
Microconidia - small single celled conidia
What is a Conidiophore?
The stalk that branch off from hyphae and have microconidia on them
What is Sproangiospores?
A type of spore: medically important single celled spores formed within sacs called sporangia from the end of special hyphae
Essentially sporangiospores are held in a sac
What causes allergic reactions?
inhalation of airborn spores
What are the two most common methods to diagnose fungi infections?
1) direct microscopic observation of the fungi (KOH technique or staining)
2) biopsy
What is the third most common technique to diagnose fungi infection?
cultivation on blood agar (at 37 degrees most commonly)
What is cyclohexamide used for in agar?
to retard growth of many nonpathogenic fungi (need to be careful because C. neoformans is sensitive to cycloheximide)
What are the targets of drugs against fungi? (4)
1) ergosterol
2) cell wall synthesis
3) nucleic acid synthesis
4) disruption of microtubules
What do polyenes do?
Targets ergosterol
What do azoles and allylamines do?
enzymatically interfere with the bio-synthetic pathway of ergosterol
What do Echinocandins do?
Target cell wall synthesis
What do antimetabolites do?
goes after nucleic acids synthesis
What does Griseofulvin do?
goes after microtubules
What is the problem with the drug flucytosine?
organisms often develop a resistance to it
What are four possible strategies of combination therapy?
1) inhibition of different stages of SAME biochemcal pathway
2) Inhibition of different fungi cell targets
3) Increased penetration of one agent into the cell because of the permeabilizing activity of another agent
4) inhibiting the outward transport (efflux) of ANOTHER agent that is meant to be inside
What are the drawbacks of combination therapy? (ways the drugs can antogonize each other)
1) action of one agent REDUCES CONCENTRATION of the target of another
2) action of one agent MODIFIES the target of another drug
3) action of one agent BLOCKS ACCESSIBILITY to target of another drug
How do fungi develop resistance? (3 ways)
1) through efflux pumps
2) alterations
3) reduced access to drug targets
fungi DOES NOT destroy or modify the antifungal drug
What is a primary resistance?
an organism that is resistant to a particular drug without prior exposure to the drug
What is secondary resistance?
An organism develops resistance to a particular drug only AFTER exposure to the drug
What is the eagle effect?
eagle effect is defined as an organism that is RESISTANT to high concentrations of the drug but SUSCEPTIBLE to low concentrations
