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Immuno/Micro/Viro > Test 3-7 Clinical Mycology > Flashcards

Test 3-7 Clinical Mycology Flashcards

1. Appreciate the importance of fungi in human disease. 2. Describe the key characteristics of fungal cells and structures. 3. Categorize fungal infections based on tissue colonization. 4. Know the risk factors for acquiring fungal infections. 5. Know common antifungal agents and their targets (mechanism of action). 6. Become familiar with the techniques used to diagnose fungal infections and identify fungal pathogens.

1
Q

fungus affects health in three ways:

A

1) allergens
2) toxin producers
3) infectious agents

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2
Q

fungi are what kind of organsim?

A
  • eukaryotic! –> QUite similar to humans
  • HAVE CELL WALL (NOT LIKE BACTERIAL NO PEPTIDOGLYCAN)
  • MEMBRANE STEROL COMPOSITION (ergosterol instead of cholesterol - target for antivirals)
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3
Q

fungal cell wall made up of which polysaccharides and function?

A
  • mannan (mannose), glucan(glucose), chitin (n-acetylglucosamine)
  • shape, rigidity, str and protection
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4
Q

fungi memrane sterol component??

A

ergosterol

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5
Q

dimorphic

A

fungi that can grow as both yeast and molds

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6
Q

yeast details

A
  • uniceulluar (spherical or ellipsoid

- reproduce via budding

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7
Q

bastocondia

A

buds are called this from budding - SURPRISE

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8
Q

molds

A
  • have hyphae (mycelium) - fuzzy hair looking things, can be long and have cross walls = septa
  • septa vs aseptate- has cross walls vs none (coenocytic)
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9
Q

vegitative mold

A

molds growing into a subrate

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10
Q

aerial mold

A

mold grows on top of a substrate

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11
Q

molds reproduction

A

-Asexual= produce conidia (reproductive unit
Micro-small ones
Macro-big ones
Chlamydo- (Arthro-) -Conidia which form within a hyphal element
-Sexual = produce spores (product of sexual union) look like conidia but got there sexually

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12
Q

mycelium

A

basically fancy term for hyphae – each little fuzzy strand of mold growing on something

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13
Q

pseudohyphae

A

basically hyphae that are connected to each other - branched like

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14
Q

fungal infection types

A
  • SUPERFICIAL MYCOSES – infection of the outermost layers of skin and hair; Examples: Pityriasis versicolor, Tinea nigra, Black and White piedra
  • CUTANEOUS MYCOSES – infection which extends deep into the epidermis as well as invasive hair and nail infections.; Examples: Dermatophyte infections; “ringworm”, “athlete’s foot”, “jock itch”
  • SUBCUTANEOUS MYCOSES – infections involving the dermis, subcutaneous tissues, muscle, and fascia.; Examples: Sporotrichosis, Chromoblastomycosis
  • SYSTEMIC MYCOSES – infections that originate primarily in the lung but may spread to any organ in the body.; Examples: Dimorphic fungi; Histoplasmosis, Blastomycosis, Paracoccidioidomycosis, Coccidioidomycosis. Cryptococcosis.
  • OPPORTUNISTIC MYCOSES – infection associated primarily with immunosuppressed individuals.; Examples: Candidiasis, Aspergillosis, Zygomycosis, Pneumocystis jiroveci pneumonia.
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15
Q

host response/Immunity to fungal

A
  • Innate immune system of a healthy individual is generally sufficient to prevent fungal infection: intact skin; pH; competition with the normal bacterial flora; epithelial turnover rate; desiccated nature of the stratum corneum; mucous membranes - antimicrobial peptides, ciliated cells
  • When these protective barriers are breached fungi gain access to, colonize, and multiply in host tissues.
  • Fungi can gain access to host tissues by traumatic implantation or inhalation.
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16
Q

The severity of disease caused by fungi depends upon

A

the size of the inoculum, magnitude of tissue destruction, the ability of the fungi to multiply in tissues, and the immunologic status of the host.

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17
Q

humoral role against fungi

A

small role

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18
Q

Which immune response is essential against fungi infection?

A

CELL MEDIATED

19
Q

Topical therapy

A

Superficial and most cutaneous infections

20
Q

Systemic therapy

A

Subcutaneous and systemic infections, some cutaneous

21
Q

most common targets with antifungals

A
  • CELL WALL- inhibitors of glucan synthesis (echinocandins) or chitin synthesis (nikkomycin)
  • CELL MEMBRANE-Inhibitors of ergosterol synthesis (azoles and allylamines)
  • DIRECT MEMBRANE DAMAGE-(polyenes)-BIND TO ERGOSTEROL
22
Q

thiocarbamates mechanism

A

inh ergosterol synthesis

-topical

23
Q

allylamines mechanism

A

inh ergosterol synthesis

24
Q

morphorlines mechanim

A

inh ergosterol synthsis

25
Q

polyene mechanim

A

-bind to ergosterol = pore formed when bound to ergosertol = leakage and fungal death

26
Q

azoles mechanism

A

inh ergosterol synthesis

-ORAL OR PARENTAL

27
Q

nucleoside analog mechanism

A

inh both RNA and DNA function and synthsis

28
Q

nucleoside analongs are most helpful/active against:

A

medically important yeasts

29
Q

downside to polyenes

A

may be toxic to host

30
Q

grisans mechanism

A 
inh mitosis (interacts with microtubules)
-ORAL
31
Q

allylamines are not effective against?

A

YEAST

32
Q

echinocandins mechansim

A
  • inh synthesis of Beta-glucans = no fungal cell wall

- HIGHLY SELECTIVE -NO TOXICITY - Humans dont have b-glucans

33
Q

potassium iodide mech

A

oldest know antifungal _ UNKNOWN MECH

34
Q

ergosterol syn or binding inh may have problems

A

because molecules are kind of similar and enezymes may be kind of similar

35
Q

laboratory diagnosis of fungi is done how

A

DIRECT VISULAIZATION OF FUNGAL ELEMENTS

36
Q

paritcularly difficult to diagnose…

A

opportunistic infection - so prevalent in environment dont know if it was just in the air or if its what is actually making patient sick

37
Q

KOH preparation

A
  • used to examine hiar, nials, skin scrapings, fluids, exudates, or biopsies
  • 10% solution of KOH –>clears host cells and leaves only the more rgid cell walls of yeast and molds
  • direct visual exam or with staining
38
Q

specialized stains for carbohydrate cell wall?

A
  • chlorazol black

- calcofluor white

39
Q

all fungi stain gram??

A

POSITIVE

40
Q

enhancing histological specimens with which stains/

A

gormori methylamine silver (GMS)

periodic acid schiff (PAS)

41
Q

india ink stain

A

FOR CAPSULE - see halo of capsule

ex) cryptooccus neoformans (fungal meningitis)

42
Q

germ tube test

A

-incubate in serum and these fungi will make germ tubes

MOST OFTEN CADIDA ALBICANS

43
Q

common agar used in the cultivation of pathogenic fungi.

A

Sabouraud dextrose agar

44
Q

why do we need special agars to grow fungi?

A
  • grow slower than bacteria
  • inh bacterial growth on plate with acidic pH or antibiotics
  • need reduced temperature

Immuno/Micro/Viro (14 decks)

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