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40 Cards in this Set
- Front
- Back
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function of fungal cell wall (3)
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shape
strength contains enzymes |
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Two basic forms of fungi
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Yeast-single cells
Mold-filaments, branch |
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What is the spitzenkorper
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where the fungal filament splits in order to branch
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What are fungal sterols and how do they differ from human cholesterol
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ergosterol C28 vs cholesterol C27
target for polyene antifungals -nystatin -amphotericin B |
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What are the main components of the fungal cell wall
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Fibrillar polysaccharides
1)chitin - beta(1-4)linked NAG's 2)fibrillar glucans NAG N-acetyl D glucosamine |
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How do yeast vs. molds distribute within the environment
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molds via spores
yeast via fluid film |
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What are some examples of dimorphic fungi
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*grow as yeast and mold
Sporothrix Histoplasma Blastomyces |
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How are fungi identified
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Via spore structure, must culture to id
Blastoconidida Thallic conidia (arthroconida) Sporangium |
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What is special about Cryptococcus capusle making it antiphagocytic
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negatively charged polysaccaride
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Polyol production occurs in the fungal cell wall,
mannitol and arabinitol what are their functions |
free radical scavengers helping protect against phagocytic killing
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What does an elevated arabinitol:creatinine indicate
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invasive Candida
*arabinitol cleared like creatinine |
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Why are dermatophytes (ringworms) only able to survive in the strateum corneum
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lack Fe chelators that transport Fe into cells
*those that do survive must battle host transferrin and lactoferrin |
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How does 5-fluorocytosine (fungicidal) work
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5-FC enters fungal cell
5-FC converted to 5-FU via deaminase *human's lack deaminase *5-FU inhibits RNA translation and DNA synthesis |
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How do polyenes work
-amphotericin B -Nystatin |
Binds to ergosterol and forms ion channels in fungal membrane
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How do azoles work
-ketooconazole -fluconazole |
Inhibits lanosterol demethylase
Blocks lanosterol to ergosterol |
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What is fungi is prone to gaining resistance Azole's
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C. Albicans
-Upregulates ABC transporter -Upregulates MDR pump -mutation in lanosterol demethylase |
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How do Echinocandins work
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inhibit beta(1-3) glucan synthetase
-important for forming carbohydrate polymers in hyphal walls |
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What species of fungi do echinocandins work on
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invasive aspergillosis and invasive or serious mucosal candidiasis
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How do the allylamines work
-terbinafine |
inhibit squalene epoxidase
blocks squalene to squalene epoxide *high activity against ringworm (accumulates in S. corneum) |
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How does Griseofulvin work
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interferes w/ microtubules and spindle formation during mitosis
(accumulates in S. Corneum) *used against ringworm |
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How does Whitfield ointment work
-salicylic acid -benzoic acid |
weak acids
1)at low pH in HA form enters fungal cell 2)higher pH of fungal cell causes ionized form of HA to accumulate |
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What are the toxic components found in mushrooms
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alpha-amanitin-inhibits RNA polymerase 2
muscarine-cholinergic poisoning ergot psilocybin ibotenic acid |
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Which is more dangerous alpha amanitin or muscarine & how do they present
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alpha amanitin-fulminant hepatitis, takes a half day to day to incubate "allows toxin to act before emesis or diarrhea"
muscarine-PSL, perspiration salivation lacrimation, rapid onset (30 min) pinpoint pupils |
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What is the etiological agent that causes tinea versicolor
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Malassezia
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Under a KOH mount what is typically seen when looking @ Tinea Versicolor
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psuedohyphae w/ budding yeast
meatballs and spaghetti |
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Will tinea versicolor fluoresce or not under wood's lamp
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Yes
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What drugs are effective against Tinea Versicolor
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Keratinolytic -propylene glycol
Selinium sulfide Azoles |
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In order to grow a culture of tinea versicolor what must be added
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lipids
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What patients are susceptible to Malassezia
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Premature infants- intralipid nutrition given via catheter
AIDS-severe folliculitis and seborrheic dermatitis |
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What are the main groups of Dermatophytes
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Trichophyton 10 species
Microsporum 5 species Epidermophyton 1 species |
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What is seen under a microscope of a dermatophyte w/ a KOH mount
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branching hyphae w/ septa may see arthrospores
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What are key enzymes Dermatophytes produce to allow for survival
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Proteinases
Sulfite- reduces disulfide bonds in keratin |
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Tinea Capitis has two main forms & what species are associated w/ these forms
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ectothrix- fluoresce in wood's lamp, stops before puberty
microsporum species endothrix- doesn't fluoresce, continues post puberty Trichophyton tonsurans |
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What are the Favus, Kerion, and Id reactions
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Favus-scarring of hair follicles
T. Schoenleinii Kerion-Boggy tumor of hair follicles w/ strong inflammatory response Id reaction- inflammation and blistering at non infected sites *no fungi found here |
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What drugs are effective against tinea capitus and onchomycosis
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azoles
griseofulvin allylamines |
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What are the 3 main types of subcutaneous infections caused by fungi
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Mycetoma
Chromomycosis Sporotrichosis |
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What causes mycetoma
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fungi or filamentous bacteria
-granules of mycelium or filamenotous bacteria seen -width of filaments distinguish actinomycetes from fungi |
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What is chromomycosis
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melanized cells is characteristic
-round body form chromoblastomycosis -hyphae form phaeohyphomycosis *looks like fine twigs |
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What is the characteristic shape of Sporothrix yeast & what is unique about it
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cigar shaped @ 37degrees
twigs w/ berries @ room temp |
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What drugs are effective against lymphocutaneous forms & systemic forms of sporothrix
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lymphocutaneous
-KI -azoles systemic "associated w/ immunosuppression & AIDS" -amphotericin B -azoles {no KI} |
