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Microbio 4 > Mycoses > Flashcards

Mycoses Flashcards

1
Q

why are mammals so resistant to fungi?

A

core body temp 37 is too high for fungi

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2
Q

why is it hard to medicate against fungi?

A

they are eukaryotic- so hard to get selectively effective drugs

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3
Q

fungi

A

eukaryotic, either unicellular or filamentous, achlorophyllous organism using absorptive nutrition. non motile

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4
Q

fungi size

A

larger than bacteria- 2-6 microns, though hypae can be long

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5
Q

two basic forms of fungi

A

yeast- oval cell that reproduces by budding or fission. growth occurs isotropic- in all directions

hypha- thread-like filament that may brunch may contain septa that divide the cytoplasm into segments, w/ each segment having a nucleus. an emerging hypha is a germ tube and occurs only at tips

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6
Q

spitzenkorper

A

collection of vesicles near the tip that is specific to hyphal growth

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7
Q

aerial v vegetative hyphae

A

vegetative- submerged w/in growth media or tissue

aerial- hyphae produce spores that are easily air born facilitating spread

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8
Q

spore

A

a reproductive propagule tht forms sexually

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9
Q

conidia

A

asexual spores classified as microconidia (small, airborne, infectious) or macroconidia (large, identifiable)

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10
Q

mycelium

A

network of numerous hyphae and spores

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11
Q

advantages of hyphal growth

A

apical growth enables fungus to extend into fresh zones

tip extension can be rapid

hyphal tips have penetrating power resulting from tugor pressure

specialized adhesins specific for preferred substrates

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12
Q

dimorphism

A

growth in two different forms.

thermal dimorphism- growth in two different forms occur at different temps

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13
Q

intermediate growth form

A

yeasts can become elongated under certain conditions

elongated yeasts are pseudohyphae

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14
Q

absorptive heterotrophs

A

requires carbon be supplied in organic form

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15
Q

sabourauds agar

A

has an acidic pH, and allow selective growth for fungi

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16
Q

general properties of the fungi cell wall

A

cell wall constitutes a large proportion of the cell mass

all medically important fungi have a cell wall

the fungal cell wall is biochemically unrelated to bacterial cell walls

the fungal cell wall contains important Ags used in diagnostic tests

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17
Q

inner fungi cell wall

A

B 1,3 and 1,6 glucan and chitn comprise most of cell wall mass and provide stability strength and rigidity

allows for the wall to expand and contract and prevent lysis

Fungal PAMP- B 1,3 glucan is a major target of antifungal immunity (dectin 1)

B 1,3 is target for blood assays

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18
Q

outer fungi cell wall

A

heavily modified w/ polysaccharides

functions

  • protect and mask inner 1,3 glucan
  • adhere to hosts and other materials
  • elicits Ab production
  • disulfied bond linkages between proteins which can be broken by bleach
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19
Q

cytoplasmic membrane

A

main distinguishing feature of fungal cell membranes is ergosterol instead of cholesterol

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20
Q

3 classes of drugs used for fungi

A

polyenes- target ergosterol directly

azoles- target fungal p450 cytochrome

echinocandins- target fungal beta glucan biosynthesis

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21
Q

drugs that affect membrane permeability

A

polyenes- amphotericin B (cidal) and Nystatin (static)

bind to sterols and damage the membranes- binds much better to ergosterol

amphotericin B- systemic
nystatin- topical or oral

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22
Q

drugs that inhibit cell membrane synthesis

A

azoles- systemic agents useful for treatment of oral thrush

ex fluconazole, ketoconazole

given orally

inhibits ergosterol synthesis via inhibition of cytochrome p450. inhibits phagocytotic PMNs and macrophages- fungistatic

23
Q

drugs that inhibits cell wall synthesis

A

echinocandins- inhibitor of glucan synthesis by inhibiting 1,3-b-D-glucan synthase

ex. caspofungin

fungicidal or fungistatic

24
Q

antimetabolite drugs

A

flucytosine- inhibits fungal protein synthesis by replacing uracil with 5-flurouracil in fungal RNA and inhibits thymidylate synthetase and thus interferes w/ fungal DNA synthesis

25
mechanisms of resistance to antifungal compounds
changes conferred by changes in the fungal genome.
26
dermatophytes
cause of skin infections epidermophyton trichophyton microsporum
27
dermatophytes properties
filamentous fungi w/ septate hyphae that invade skin, hair and nails
28
dermatophytes pathogensis
spreads via fragmented, infected cells come into contact w/ uninfected. also spread thru fomites on combs, brushes, and hats. grows best in warm, moist, humid environment
29
dermatophyte clinical features
name: tinea + latin term of affected body part infections of the skin may be red and inflammed crumbling of nails and skin around nails w/ itching hair may break and fall off
30
dermatophyte epi
found in children in daycare, groups sharing locker room spaces risk factors: male, age, nail trauma, poor circulation
31
dermatophyte diagnosis
direct examination via KOH mount woods ultraviolet light detects ectothrix infections
32
dermatophyte culture
plated and growth after 1-2 weeks identified by appearance
33
dermatophyte treatment
geared towards body part infected griseofulvin and traizoles
34
sporotrichosis dimorphism
grows as a budding yeast at 37 hyphae at 25 degrees
35
sporotrichosis pathogenesis
introduced via puncture grows locally in subcutaneous tissue but spread
36
sporotrichosis clinical features
lesions initiate as surface placques with irregular borders may spread to proximal lymphatics after 3 weeks, nodular lesions emanate from site of inoculation
37
sporotrichosis epi
grows on vegetables in mold form makes farmers at risk
38
sporotrichosis diagnosis and treatment
diagnosis by clinical suspension and isolatoin of S. shenkii cultures treatment- antifungals
39
chromomycosis epi
skin and subq infections caused by a variety of soil fungi most common in tropical and subtropical America
40
chromomycosis pathogenesis
slow growing wart like lesions containing brown fungal cells are seen following abrasion with plant material containing fungi local host reaction involves a hyperplastic inflammatory response that contributes to lesion formation
41
chromomycosis clinical features
initial lesions is a single nodule with scaling at the site of inoculation after months/years, new nodules and verrucous plaques appear. over time, lesions become large and cauliflower like that bleed easily
42
chromomycosis diagnosis and treatment
diagnosis- biopsy and histologics treatment- surgical removal
43
mycetoma
chronic infection of skin and sub q caused by madurella species. similar to actinomyces
44
mycetoma pathogenesis
organisms implanted via penetrating skin injury caused by trauma may persist for many years w/o disease eventually inflammatory mass develops
45
mycetoma epi
adults exposed during outdoor activites
46
mycetoma diagnosis
grains in tissue distinctive shape- cultures azoles or surgeries needed
47
immunity to subq mycoses
cell mediated immune responses are important for inhibiting spread w/o immunity, can cause life threatening disease
48
candida most common cause of life threatening fungal infections in patients who are: immunocompromised invasive procedures major trauma
ok
49
candida clinical features
normal inhabitant of mucous membranes and GI tracts causes "diaper rash", thrush, esophogeal candidiasis, and vaginitis
50
candida characteristics
budding at yeast at room temp. at 37 it extends into hyphae. ability to form germ tubes w/in hour is indicative of c. albicans vegetative
51
candida glabrata
second most prevalent yeast pathogen in humans grows in yeast form only
52
candida pathogenesis
source of infection is patients endogenous organism, tho person to person is possible Antibiotics knock out cell mediated immunity, increases number of candida. attachment occurs via hyphae and invasion of keratinocytes follows ability to switch between growth forms is virulence factors fungicemia may occur following extensive colonization forms biofilms on catheters
53
candida immunity
DTH skin testing to candida is always positive in immunocompetent individuals and is used to test immunocompetency both innate and adaptive contribute to candida defense Th17 cells very important by increasing PMNs and other antimicrobial peptides
54
candida epi
most infections occur in developed countries newborns acquire albicans from mom occurs in immunosuppressed- HIV, chemo occurs with catheters- biofilms

Microbio 4 (5 decks)

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