MCM 2-41 Pathogenic Fungi Flashcards Preview

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Flashcards in MCM 2-41 Pathogenic Fungi Deck (39)
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1

what is the main issue with fungi treatment?

we are more similar to fungi than we are to bacteria. there is a lot of "toxic spillover" with antifungal medications that can effect those similar structures in humans

2

hardiness of bacteria vs fungi

fungi can grow in colder, dried, more acidic, and more osmotically hihg pressure areas (high osmotic pressure jelly in the fridge growing mold)

3

two major types of fungi

Yeast - simple single cells, reproduce via budding

mold - more complicated, grow as filaments (hyphae) and form mat (mycelium). growth occurs at tip of filament. asexual and sexual structures


both do mitosis

4

fungi undergo mitosis (TF)

True - however fungi undergo a "closed" mitosis meaning that the nuclear envelope does not disperse - harder to see in microscope

5

sexual or asexual molds are more clinically relevant?

what is important for microscopic diagnosis?

asexual molds

distinct appearance of spores

6

prokaryotes are ___ by definition, fungi are ______

prokaryotes are bacteria

fungi are eukaryotic heterotrophs like humans

7

What must antifungals target? why?

fungi do not have 70s ribosomes or peptidoglycan walls

antifungals must target beta-glucan walls and ergosterol in the membrane

8

TF Antifungals often have some toxicity in humans, and there are many fewer molecular targets available

true - many of their molecules are too similar to ours

9

why are there more cutaneous fungal infections and food spoilage?

fungi can live in the fridge and survive on the hostile enrivonment of the skin because they can can grow in drier, higher-osmotic-pressure, and colder environments than bacteria

10

five types of asexual spores, called ____, have what?

conidia

distinctive microscopic appearances used for diagnosis

11

Thermal dimorphism

: several important fungal pathogens grow as mold at 24C and as yeast at 37C. Yeast form has more immune-evasive properties; dual cultures can be useful for diagnosis.

12

immune response to fungal infection?

granulomatous, sometime also suppurative (pus forming and discharge)

13

most fungal pathoens are...

environmental - little contagion or drug resistance, no eradication
Exception: C. albicans yeast is normal flora / opportunistic pathogen

14

Mycotoxicosis

caused by eating fungal toxins (wrong mushroom or spoiled food); not fungal infection.

15

fungal infection can be diagnosed by

PPD, KOH-mount microscopy with fungal stains, culture on Sabouraud’s agar.

16

major classes of antifungals

are polyenes (disrupt fungal cell membranes at ergosterol insertion sites), azoles (inhibit ergosterol synthesis), echinocandins (inhibit beta-glucan synthesis)

17

polyenes
what do they do?
toxicity?
examples?
treats which fungi?

disrupt cell wall membranes at ergosterol insertion sites
highly effective and broad-spectrum but toxic – Amphotericin B is the only systemic and is nephrotoxic

18

azoles
what do they do?
toxicity?
examples?
treats which fungi?

inhibit ergosterol synthesis

are less toxic; different ones optimally active against different fungi; Fluconazole/Diflucan major one, treats candidiasis and cryptococcosis

19

Echinocandins
what do they do?
toxicity?
examples?
treats which fungi?

inhibit beta glucan synthesis

are low-toxicity, highly effective against candida and aspergillus

examples end in "-fungin"

20

superficial mycoses

symptoms?
treatment?

caused by fungal grown on superficial skin layer. does not require thermal dimorphism

very common - symptoms are minor; itch or discoloration. treated with topical azoles (fluconazole, diflucan)

fluconAZOLE

21

dermatophytosis


example?

symptoms called?
tranmitted by?
diagnosed with?
treatment?
thermal dimorphism?

example of superficial mycoses


athletes foot - "dermatophytosis" caused by three different fungi genera
infect only superficial keratinized structures via keratinases

symptoms are called tinea

transmitted by fomites or autoinnoculation


diagnose with KOH mount, culture

treat all body sites simultaneously with topical azole

22

subcutaneous mycoses

spread pattern?
thermal dimoprhism?
history of?

treatment

introduced by trauma exposing subcuntenous tissue to soil or vegetation.

slow spread from trauma site towards trunk by lymphatics
-thermal dimorphism

history of ineffective antibiotic treatment

treatment with oral azoles.
serioues cases may require amphotericin B and local surgery

23

sporotrichosis

thermal dimorphism?
transmission?
spreading?

diagnose?

treatments?

example of subcutaneous mycoses
caused by sporothrix spp

thermal dimosphism
enters skin through small injuries like throns/splinters

painless ulcer at site spreads up lymphatics over years

if immunocompromised - may be dissemintated meningitis

diagnose biospy and culture at room temp from pus (turn it from yeast form to mold form)

treat normal type with oral azoles
more serious forms with amphotericin B

24

Systemic Mycoses

tramission?
thermal dimosphism?
severity?
problem?

these are environmental spores/fungi in soil that get inhaled into the lungs. not person to person

thermal dimorphism

range of severity - asymptomatic to death

may mimic TB, but source is american dirt not foriegn crowds

25

Histoplasma

thermal dimorphism?

endemic areas?

transmission?

symptoms?

diagnosis?

treatment?

example of a systemic mycoses

thermally dimorphic with mold/yeast forms

endemic to ohio, missouri, mississippi

soil based infectious microconidia (micro spores) kicked up

causes pulmonary symtpoms
previously healthy - clear or granulomas
higher dose - TB mimic
CMI deficient host disseminates in macrophages (yeast survive lysosomal fusion by producing ammonia). look for pancytopenia and tongue ulcerations

diagnosis - history is critical, biopsy for yeast in macrophages, cultures for dimorphism, ELISA for antigen

treat serious lung w/ itraconazole, meningitis with fluconazole, disseminated with amphotercin B

26

Opportunistic mycoses

diseases/severity widely varied, depends on pre-exisitng conditions.

optimal treatment addresses infection an the underlying problem

27

cryptococcosis

typical patient?

symptoms?

treatment?

environmental
enabled by reduced CMI, suppresses host inflammatory response

presents late in disease with meningitis and skin nodueles or pulmonary symtpoms

diagnose by CSF or "CRAG"

treat in combo with of flucytosine and Amphotericin B initially, then long-term fluconazole.

28

histoplasma of immunocompromised vs immunocompetent

previously-healthy usually clear or contain in granulomas, higher-dose infection produces TB mimic, CMI-deficient host disseminates in macrophages (yeast survive lysosomal fusion), look for pancytopenia and ulcerations on tongue.

29

how do histoplasma disseminate?

enter phages, survive lysosomal fusion, spread to sites in body

30

main diagnostic for cryptococcosis?

Oval - big thick capsule (KEY). Important virulence factor (hard for phags to engluf) and good for diagnostic.

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