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FOH Final > 6.6 Medical Mycology > Flashcards

6.6 Medical Mycology Flashcards

1
Q

Are fungi Eukaryotic or prokaryotic?

A

Eukaryotic with organelles and nucleus

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2
Q

What molecule is in the cell membrane of Fungi?

A

Sterols present (ergosterol)

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3
Q

What molecules are present in the cell wall of fungi?

A
  • Polysaccharides including chitin
  • Polymer of N-acetylglucosamine
  • alpha-1,3 glucan (not in humans) Target for drugs
  • beta-1,3-glucan (not in humans)
  • Galactomannan
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4
Q

What is the 02 utilization methods for Fungi?

A

aerobic to obligate anaerobes

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5
Q

What is the doubling time of Fungi?

A

usually hours, more complex than bacteria that can double in minutes.

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6
Q

What are the functions and reproduction methods of spores in fungi?

A
  • Mainly asexual, but can reproduce sexually

- Functions include survival and dissemination

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7
Q

What percent of infections are fungi related and why have the number of diagnosis increase over the recent years?

A
  • 20% of infections are fungus related

- Increased diagnosis due to more immunosuppressed and better at diagnosis

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8
Q

What are risk factors for fungal infections?

A
  • Living in a warm, humid climate
  • Occupational (outdoor jobs, landscaper)
  • CMI deficiency
    • Cell mediated immune issues/defects
    • Higher incidence more intractable
    • Neutrophil, T-cell mediated response most important.
  • Mostly environmental, not endogenous
  • Some are normal microbicota
  • Infections tend to be subacute to chronic, not usually acute
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9
Q

What are the three types of mycoses?

A

1) Superficial/cutaneous
2) Subcutaneous
3) Systemic

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10
Q

Describe Superficial/cutaneous fungi infections

A
  • hair, skin, nails

- most common

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11
Q

Describe Subcutaneous mycoses

A
  • beneath the skin

- Rare, tropical (Mexico)

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12
Q

Describe Systemic mycoses

A
  • Deep within body
  • Characteristic geographic regions (endemic mycoses)
  • Coccidioides immitis, southwestern U.S., Mexico, Central and South America
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13
Q

Describe Opportunistic Fungi

A
  • Only in immunocompromised, debilitated, or break in skin or mucous membrane
  • Normal microbiota or environmental fungi
  • Aspergillosis, candidiasis, cryptococcosis, mucormycosis
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14
Q

Describe Primary Pathogens Fugi

A
  • Infects healthy individuals
  • Examples: Histoplasmosis, blastomycosis, coccidioidomycosis, paracoccidioidomycosis
  • Only environmental, soil, or vegetation
  • Can be inhaled causing lung infections
  • Conidia or hyphal fragments
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15
Q

Describe Unicellular Yeast

A

1) Unicellular eukaryotes
2) round/oval, look like bacterial colonies on agar plates.
3) ~10 times bigger than bacterial cells
4) Usually reproduce by budding
5) Divide asymmetrically
6) Buds= blastoconidia
7) May fail to detach or form a short chain of cells called pseudohypha

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16
Q

Describe multicellular molds

A

1) Multicellular, filamentous eukaryotes
2) Branching cylindric tubules called hyphae that can penetrate tissues. These grow from the tips and are multinucleate.
3) Mass of hyphae=mycelium
4) Part of mycelium involved in gaining nutrients=vegetative mycelium
5) Part of mycelium is involved in growth and reproduction

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17
Q

What is macroconidia?

A

Relatively large, complex conidia

18
Q

What is microconidia?

A

Smaller, more simple conidia

19
Q

What is a sporangium?

A

Sack that sporangiospores are in

20
Q

Are conidia in a sack?

A

No

21
Q

Conidiophore(stem) spores are called?

A

Conidiospores (no sack)

22
Q

Sporangiophore(stem) spores are called?

A

Sporangiospores (sack surrounds spores)

23
Q

Describe Dimorphic Fungi

A
  • At low temperature in the soil the fungi grows as a filamentous fungus (mold)
  • After being inhaled into the lungs the dimorphic fungi undergoes a morphological switch triggered by the change in temperature and become yeast like.
  • can form hyphae in vivo and penetrate/spread
  • Affects expression cell wall glycoproteins, proteolytic enzyme secretion, susceptibility to oxidative damage in neutrophils, adaptation to new environments.
  • Makes harder for human immune system to fight due to switching.
24
Q

What is a Blastoconidia?

A

Buds formed by yeast

25
Q

What is a Pseudohyphae?

A

Branching cylindric tubules

26
Q

What are Septate?

A

Having or partitioned by a septum or septa.

27
Q

What is Coenocytic?

A

An organism made up of a multinucleate, continuous mass of protoplasm enclosed by one cell wall, as in some fungi or algae.

28
Q

What is Mycelium?

A

Mass of Hyphae

29
Q

What are the function of Fungal spores?

A

Reproduction, survival, and transmission

30
Q

What is the top virulence factor in fungi?

A

Dimorphism

31
Q

What are some other virulence factors in fungi?

A

1) Adhesins
2) Proteases, elastases, phospholipases (cut through tissues
3) Some resist killing in macrophages
4) Sidrophores
5) Biofilms

32
Q

What is the main way that fungi cause injury to the body?

A

Injury is largely due to destructive aspects of delayed type hypersensitivity (DTH) response as result of immune system being unable to clear. Cell mediated response like TB

33
Q

Which fungi has a capsule?

A

Cryptococcus neoformans. In environment it lacks capsule, but gains it when infecting humans.

34
Q

How do you stain a fungi capsule?

A

Negitive stain with India ink

35
Q

What is siderophores?

A

A molecule that binds and transports iron in microorganisms.

36
Q

What does a high alpha 1,3-glucan content in yeast walls do as a virulence factor?

A

Helps mask other immunogenic molecules.

37
Q

What is the best rapid, cost-effective diagnosis of fungal infection?

A

Direct microscopic examination of clinical specimens.

38
Q

What stains and chemicals are used on fungi?

A
  • 10% KOH

- Stains: Lactophenol cotton blue, Gram, silver, calcofluor white (fluorescent).

39
Q

What Gram stain do most fungus stain as?

A

Gram positive

40
Q

What is common yeast morphology?

A
  • Size, wall thickness, capsule present/absent
  • Size, shape, appearance, spores
  • Hyphae, septate, or coenocytic, type branching.
41
Q

What are two typical media for clinically important fungi?

A
  • SDA= Sabouraud Dextrose Agar

- SABHI- Sabouraud dextrose media+ BHI media

42
Q

What is a molecular way to identify different species of fungi?

A

Each species of pathogen carries unique DNA or RNA signature that differentiates it from other organisms. Examples: Nucleic acid amplification, nucleic acid probes, and microarrays. Fast sensitive specific.

FOH Final (32 decks)

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