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CMBM 3 > Medical Mycology > Flashcards

Medical Mycology Flashcards

1
Q

What are the characteristics of fungus?

A 
eukaryotic
contain a nucleus
contain membrane bound organelles
Heterotrophic
-lack chlorophyll (not autotrophic)
- saprophytes (feed on living and dead organic matter) or parasitic (utilize living tissue)
Thermally dimorphic (mostly) - can exist in different forms based on temperature 
Kingdom - Mycota
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2
Q

Which agent is associated with Meningitis in the immunocompromised?

A

Cryptococcus

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3
Q

What is the structure of the fungus?

A

Cell wall - antigenic, multilayered
- Polysaccharides (chitin, chitosan, cellulos, glucan, mannan)

Cell membrane:

  • bilayered made of phospholipids and sterols (ergosterol, zymosterol)
  • protects the cytoplasm and facilitates capsules and cell wall synthesis

Cytoplasm:
-nucleolus, ER, mitochondria

Polysaccharide Capsule -***Cryptococcus neoformans

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4
Q

What is the encapsulated yeast we are supposed to know?

A

Cryptococcus neoformans

  • antiphagocytic
  • agglutination reaction
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5
Q

What is thermal dimorphism?

A 
Two different forms based on temperature
Yeast (at 37 degrees)
- unicellular
- reproduces asexually by budding
- also sexually >>>basidiospore
- India ink can be used to identify
- all yeasts are aerobic and grows at wide range of temperature

Filamentous (Mold)

  • multicellular
  • vegetative growth of filamentous
  • aerobic filamentous fungi
  • mass of hyphae make up “Mycelium”
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6
Q

What is a septae hyphae?

A

hyphae separated by septum

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7
Q

The spores will become (mold/yeast).

A

mold

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8
Q

Distinguish between pseudohyphae, non-septate, and septate?

A

Non-septate (coenocytic)
Septate
Pseudohyphae (lack cytoplasmic connections between cells)

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9
Q

What does pathogenesis depend on?

A

immune response

structure of fungus

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10
Q

What will a fungal infection cause?

A

granuloma somewhere

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11
Q

How are fungal infections transmitted?

A

environment

Most are not communicable (except dermatophytes)

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12
Q

What agars are used to identify fungus?

A

Sabouraud’s agar
Blood agar
microscopy

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13
Q

What do the antifungal drugs work on?

A

Ergosterol synthesis (makes up cell membrane)

  • allylamines
  • azoles
  • morpholines
  • polyenes
  • amphotericin B (lots of side effects)
  • nystatin
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14
Q

What are 4 types of fungal infections?

A

superficial
subcutaneous
systemic
opportunistic

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15
Q

What subcutaneous infection do we need to know?

A

sporothrix schenckii

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16
Q

What does superficial mycoses affect?

A

epidermis at the stratum corneum layer

  • not invasive
  • normally no pathological change
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17
Q

How is dermatophyte diagnosed?

A

Branched hyphae on KOH wet mount
-culture - myobiotic sugar
-Sabourand’s dextrose sugar
Wood’s light

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18
Q

All dermatophyte infections are caused by members of what 3 genera?

A
  • microsporum
  • epidermophyton
  • tricophyton
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19
Q

What is tinea corparis?

A

ringworm (trunk, arms, legs)

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20
Q

What is tinea cruris?

A

jock itch (groin)

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21
Q

What is tinea pedis

A

athlete’s foot

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22
Q

tinea capits

A

ringworm of scalp

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23
Q

Tinea unguium

A

nail fungus

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24
Q

Tinea manus

A

ringworm of hand

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25
Q

What is white piedra caused by?

A

Tinea blanca

Trichosporon beigelii

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26
Q

What is black piedra caused by ?

A

Piedra hortae

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27
Q

What treatments are available topically? oral?

A

topical (miconazole, clorthrimazole)

oral (Griseofulin, Ketaconazole)

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28
Q

What is the name of the organism that causes pityriasis versicolor?

A

Malassezia furfur

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29
Q

How is Malassezia furfur diagnosed?

A

presence of branched hyphae resembling spaghetti and meatballs

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30
Q

How does the Malassezia furfur yeast appear?

A

spherical on KOH mount

31
Q

Who is at risk for Sporothrix schenckii?

A

golfers, rose gardeners, landscapers

32
Q

What is the distribution of Sporothrix schenckii?

A

world wide, mainly in tropical areas

33
Q

How is Sporothrix schenckii transmitted?

A

traumatic implantation

34
Q

What does Sporothrix schenckii cause?

A

Rose Gardener’s disease

Sportrichosis

35
Q

What can candida albicans cause orally?

A

thrush

36
Q

What fungus can be transmitted person to person?

A

candida albicans

37
Q

How are systemic fungal infections transmitted?

A 
inhalation 
thermally dimorphic
-to lung
-will give rise to yeast in body- single cell and budding
**not communicable
38
Q

What happens when macrophage encounters yeast?

A

granuloma will form

chest x-ray will show consolidation

39
Q

Describe Histoplasma capsulatum’s geographical location.

A 
Geographical distribution (Ohio-Mississippi River valley)
loves nitrogen in soil
40
Q

Where is Histoplasma capsulatum found?

A

bat, pigeon, and chicken droppings

41
Q

Who is at risk for Histoplasma capsulatum?

A

access to chicken coops, spelunking

42
Q

How would you diagnose Histoplasma capsulatum?

A

yeast is budding with narrow base***
KOH and Parker Ink
Look for H- Antigen

43
Q

What will happen in 95% of cases of Histoplasma capsulatum?

A

nothing

44
Q

Clinical symptoms of Histoplasma capsulatum may resemble what disease?

A

TB pneumonia

45
Q

Where is Blastomyces dermatitidis geographically located?

A

East of Mississippi River Valley

Central America

46
Q

Where is Blastomyces dermatitidis found in nature?

A

soil, rotten wood

beaver dam

47
Q

Describe the structure of Blastomyces dermatitidis ,

A

Round yeast with double refractive wall and single broad based budding

48
Q

What does Blastomyces dermatitidis cause?

A

Chicago disease
fever
night sweats
cough up blood

49
Q

Which fungus is the most endemic?

A

Coccidiodes immitis

50
Q

Where is Coccidiodes immitis geographically located?

A

SW United States

San Joaquin valley

51
Q

Why is Coccidiodes immitis so important?

A

transmission is via a spherules through inhalation of arthrospore
-sac ruptures and releases

52
Q

What is the geographic location of Paracoccidiodes

A

Rural Latin America and some of South America

53
Q

What has multiple, narrow base budding yeast cells

“steering wheel”?

A

Paracoccidiodes brasiliensis

54
Q

What population would be susceptible to Cryptococcus neoformans?

A

immunocompromised

AIDS patients

55
Q

Where is Cryptococcus neoformans found?

A

associated with soil contaminated with pigeon droppings

56
Q

Which fungal organism causes meningitis?

A

Cryptococcus neoformans

57
Q

How would you confirm Cryptococcus neoformans?

A

lumbar puncture

CSF culture

58
Q

Which organism stains with India ink?

A

Cryptococcus neoformans (encapsulated)

59
Q

How is Cryptococcus neoformans transmitted?

A

inhalation» colonizes the lung»lung injury

“Cryptococomas”

60
Q

What disease can result from Candida?

A

diaper rash

endocarditis (IV drug users)

61
Q

What pH does Candida require?

A

pH 7.4

62
Q

Which bacteria can maintain the pH so that Candida cannot grow?

A

lacto bacillus

63
Q

When is esophageal candidiasis seen?

A

immunodeficiency

64
Q

What population does Disseminated candidiasis affect?

A

immunocompromised

IV drug users

65
Q

Where is Aspergillus funigatus found?

A

world wide

66
Q

In the body and environment Aspergillus funigatus exists in what form?

A

acute angle hyphae form with septae
flowering head
(no head, no thermal dimorphism)

67
Q

How is Aspergillus funigatus transmitted?

A

inhalation or traumatic inoculation of conidia

68
Q

What are the signs and symptoms of Aspergillus funigatus?

A

release of mycotoxins»»mycotoxicosis
Aflatoxin via corn or nuts

Ergots

69
Q

Where does Aspergillus funigatus colonize?

A

preformed cavities and debilitated tissues

70
Q

Zygomycosis is associated with what 3 species?

A

Rhizopus
Mucor
Rhizomucor abisdia

71
Q

Zygomycosis is seed in what population?

A

immunocompromised
old
diabetic

72
Q

How would Zygomycosis appear under a microscope?

A

hyphae with wide branches, no septae

73
Q

What causes fungal pneumonia?

A 
Pneumocystis jiroveci (AIDS defining illness)
CD4 count < 100
74
Q

What are risk factors for Pneumocystis jiroveci ?

A 
CD4  < 200 cells/uL
Prior PCP infection
oral thrush
recurrent bacterial pneumonia
HIV

CMBM 3 (28 decks)

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