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40 Cards in this Set
- Front
- Back
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What are some common features of fungal infections...
a. Time scale b. Exogenous vs. endogenous c. Communcable? |
a. Chronic, long time scale
b. exogenous mostly c. non-communicable mostly |
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In what ways are Fungi different from bacteria?
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Fungi = eukaryotes --> nucleus, mitochondria, organelles, 80s ribosomes
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In what ways are fungi different from human cells?
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Have a cell wall made of glucans and chitin
Produce filamentous structures/spores |
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In what ways are fungi different from plants?
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Hetertrophic -
Most are saprobic, obtain nutrition from dead organic matter |
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What is the role of the capsule in the fungi that have it?
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Polysaccharide capsule is antiphagocytic, confers virulence
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What is contained in the cell wall?
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Complex polysaccharides
1. Chitin = polymer of N-acetylglucosamine 2. Glucans = polymer of D glucose, B-1,3 glucan is a drug target |
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What targets B-1,3 glucan?
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Echinocandins
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What is external to the cell wall?
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Mannoprotein polypeptides - mannose polymerized to polypeptides
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What is the difference between fungi and mammalian cells in terms of the plasma membrane?
Functions? (3) |
Mammalian = use cholesterol
Fungi = use ergosterol Protect cytoplasm Reglulate intake/secretion of solutes Cell wall synth |
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What are some drugs that target ergosterol and how do they do it?
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Azoles and allylamines interrupt synthesis of ergosterol
Polyenes bind ergosterol in the membrane and disrupt membrane function |
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Physiology
a. Respiration b. Metabolism c. Growth time |
a. aerobic
b. hetertrophic - depend on organic nutrients c. grow slowly (doubling time is in hours) |
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What are yeast?
2 examples |
Unicellular fungi, reproduce by budding, produce soft colonies in culture
candida and cryptococcus |
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What are moulds?
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Multicellular with elongated hyphal structures with attached conidia (spore)
Produce cottony colonies (mycelia) in culture |
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What are dimorphic fungi?
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Alternate between yeast (37 deg, mammalian host) or mould (25 deg, soil)
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What are 'perfect' fungi?
2 examples |
Perfect fungi have sexual or asexual forms that have been identified
saccharomyces cerevisiae, cryptococcus neoformans |
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How do yeast look microscopically?
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Small, oval/round
Reproduce by budding to form hyphae or pseudohyphae (string of attached yeast) |
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How do yeast look macroscopically?
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Pasty colonies like bacteria
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How do moulds look microscopically?
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In hyphae (septate or aseptate) with spores (conidia - allows for dissemination)
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How do moulds look macroscopically?
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Cottony, woolly, granular
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What are 2 mechanisms y which conidia develop from hyphae?
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blastic = budding
thallic = transformed from a pre-existing hyphal element |
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What are arthroconidia?
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Thallic conidia
Conidia break loose from each other, initiate another cycle of reproduction by germination and apical extension of growth |
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What are blastoconidia?
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Blastic chonidia in yeast
Blastoconidia of yeast grows, elongates into sausage-shaped filament called pseudohyphae (conidia fail to separate) |
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What are macroconidia/microconidia?
One disease association? |
Production of conidia of large of small forms
Tinea infections |
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What are sporangiospores?
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Produced by cytoplasmic cleavage within a spore sac (sporangium) from neoseptate hyphae
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What are superficial/cutaneous mycoses?
Example infection |
fungi colonize and grow on cutaneous epidermis, caused by dermatopytes
Tinea versicolor |
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What are subcutaneous mycoses?
Caused by? |
Confined to subcutaneous tissue --> form deep, ulcerated skin lesions
Caused by soil saprohytes that enter body through trauma |
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What are systemic mycoses?
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Inhaled dimorphic fungal conidia --> systemic mycoses
Characteristically endematous to various regions of the world |
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What are 3 fungal agents causing systemic mycoses?
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Histplasma, Blastomyces, Coccidioides
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What are opportunistic mycoses?
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Usually avirulent, but cause diseases in immunocompormised hosts
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Cryptococcus neoformans
a. type of fungus b. disease c. opportunistic disease |
a. encapsulated yeast
b. pneumonia c. meningitis in aids |
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What are 4 modes of acquisition of fungi?
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1. Inhalation of airborn conidia
2. Penetration through skin (subcutaneous mycosis) 3. Mucosal colonization and overgrowth (endogenous) 4. Contact |
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What are 2 factors that determine the course of infection?
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1. Size of inoculum
2. Natural resistance to infection |
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What is the normal cell response to fungal infection?
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Neutrophil recruitement, alveolar macrophages --> phagocytosis
In patients with severe neutrophenia, invasive fungal infections |
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How does HIV infection alter the course of P. jiroveci?
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Alters the mannose receptor-mediated binding and phagocytosis of p. jiroveci by alveolar macrophages
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What 3 modifications do cryptococcus and histoplsma undergo during an invasion?
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1. Increased metabolic rate
2. Modified metabolic pathways 3. Modified cell wall structure |
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What 2 factors control multiplication of intracellular yeast?
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1. Activated macrophages --> IFN-gamma, cytokines --> clinical manifestations (fever, fatigue, weight loss)
2. Granulomatous inflammation --> giant cells, lymphocytes (Tcyt) --> produces pathological symptoms (calcified fibrinous granuloma) |
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What is KOH staining?
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Method of visualizing superficial skin infections
KOH dissolves most of host and fungal tissue except fungal cell wall; apply to skin scrapings |
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Gimsa stains...?
Silver stains? |
Cell walls
Use Silver GMS when Giemsha not optimal |
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How can culture be used to determine fungal infection?
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Use mycological agar = saboroud dextrose
When dimorphic fungi suspected, 2 sets of plates --> 25 and 37 degrees |
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How do yeast look on plates?
Moulds? What dye is used? |
Yeast = large, moist, white/tan
Moulds = fuzzy Lactophenol blue |
