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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
Q

mechanisms of resistance to antifungal compounds

A

changes conferred by changes in the fungal genome.

26
Q

dermatophytes

A

cause of skin infections

epidermophyton
trichophyton
microsporum

27
Q

dermatophytes properties

A

filamentous fungi w/ septate hyphae that invade skin, hair and nails

28
Q

dermatophytes pathogensis

A

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
Q

dermatophyte clinical features

A

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
Q

dermatophyte epi

A

found in children in daycare, groups sharing locker room spaces

risk factors: male, age, nail trauma, poor circulation

31
Q

dermatophyte diagnosis

A

direct examination via KOH mount

woods ultraviolet light detects ectothrix infections

32
Q

dermatophyte culture

A

plated and growth after 1-2 weeks

identified by appearance

33
Q

dermatophyte treatment

A

geared towards body part infected

griseofulvin and traizoles

34
Q

sporotrichosis dimorphism

A

grows as a budding yeast at 37

hyphae at 25 degrees

35
Q

sporotrichosis pathogenesis

A

introduced via puncture

grows locally in subcutaneous tissue but spread

36
Q

sporotrichosis clinical features

A

lesions initiate as surface placques with irregular borders

may spread to proximal lymphatics

after 3 weeks, nodular lesions emanate from site of inoculation

37
Q

sporotrichosis epi

A

grows on vegetables in mold form

makes farmers at risk

38
Q

sporotrichosis diagnosis and treatment

A

diagnosis by clinical suspension and isolatoin of S. shenkii cultures

treatment- antifungals

39
Q

chromomycosis epi

A

skin and subq infections caused by a variety of soil fungi

most common in tropical and subtropical America

40
Q

chromomycosis pathogenesis

A

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
Q

chromomycosis clinical features

A

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
Q

chromomycosis diagnosis and treatment

A

diagnosis- biopsy and histologics

treatment- surgical removal

43
Q

mycetoma

A

chronic infection of skin and sub q caused by madurella species. similar to actinomyces

44
Q

mycetoma pathogenesis

A

organisms implanted via penetrating skin injury caused by trauma

may persist for many years w/o disease

eventually inflammatory mass develops

45
Q

mycetoma epi

A

adults exposed during outdoor activites

46
Q

mycetoma diagnosis

A

grains in tissue distinctive shape- cultures

azoles or surgeries needed

47
Q

immunity to subq mycoses

A

cell mediated immune responses are important for inhibiting spread

w/o immunity, can cause life threatening disease

48
Q

candida most common cause of life threatening fungal infections in patients who are:

immunocompromised
invasive procedures
major trauma

A

ok

49
Q

candida clinical features

A

normal inhabitant of mucous membranes and GI tracts

causes “diaper rash”, thrush, esophogeal candidiasis, and vaginitis

50
Q

candida characteristics

A

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
Q

candida glabrata

A

second most prevalent yeast pathogen in humans

grows in yeast form only

52
Q

candida pathogenesis

A

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
Q

candida immunity

A

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
Q

candida epi

A

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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