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Microbio Part 2 > Kinzy - Intro To Fungi > Flashcards

Kinzy - Intro To Fungi Flashcards

1
Q

What are some important. Genera characteristics of fungi?

A

They are eukaryotic - makes it difficult to selectively target fungi in the body.
Thick, rigid, cell walls - make it difficult to get drugs in.
Source of many allergies
Saprophytic - secrete enzymes that break down organic matter around them and then transport the molecules into their cells.
Form spores
Our defense is usually via neutrophils - neutropenic patients are very susceptible.
Ergosterol replaces cholesterol in membranes

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2
Q

5-fluorocytosine

A

Gets converted to FdUMP, a dTMP analogue. This is toxic for the fungus.

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3
Q

Membrane inhibitors

A

Take advantage of the fact that fungi have ergosterol whereas mammalian cells have cholesterol.

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4
Q

Polyenes

A

Bind to ergosterol in the membrane and increase membrane permeability. This allows for the loss of small molecules from the cell.

  • amphotericin - systemic infections
  • Nystatin - used only topically due to toxicity
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5
Q

Azoles

A

Interfere with synthesis of ergosterol.

- end in “Azole”

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6
Q

Echinocandins

A

Block synthesis of cell-wall polysaccharides

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7
Q

Pentamidine

A

Used against pneumocystis carinii which is common in AIDS patients.

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8
Q

What are the four major groups of fungi?

A

Zygomycetes
Ascomycetes
Basidiomycetes
Fungi imperfecti

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9
Q

Zygomyces

A

Forms a sporangium, which is essentially a big bag full of haploid spores formed by meiosis.

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10
Q

Ascomyces

A

Starts with a single cell that undergoes meiosis and the resulting four haploid spores are contained in a sac derived from the wall of the original diploid cell.

  • Think that A is the first letter in the alphabet and it starts from 1 cell.
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11
Q

Basidiomycete

A

Sexual spores bud from tip of club-shaped terminal cell.

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12
Q

Fungi imperfecti

A

No meiotic stage known. Also known as deuteromycete.

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13
Q

How to identify fungi?

A
  • in a culture they are not fastidious so they will grow on pretty much anything
  • typically though we grow them on what is called a Saboraud agar, which is broth based and has glucose.
  • whether it is pigmented (dematiciaceous) or not (hyaline) is a big deal
  • serology is important - seeing which antibodies we have circulating around. This isn’t always useful because we may have antibodies anyway in our body for some of these
  • therefore treatment is usually more dependent on site than on species.
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14
Q

What is the name of the agar that we grow fungi on generally?

A

Saboraud

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15
Q

How do Yeast multiply?

A

Budding

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16
Q

What do yeast look like in culture?

A

Smooth and creamy colonies

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17
Q

How do molds multiply?

A

They elongate and form a filament called a hypha. A mass of hyphae is called a mycelium.

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18
Q

Hypha

A

Filament of mold

19
Q

Mycelium

A

Mass of hyphae

20
Q

What does mold look like in culture?

A

Large, fuzzy, colonies that are often pigmented.

21
Q

How do pseudohyphae multiply?

A

Basically is multiplies like a yeast but they stay attached. This causes them to look a lot like a hyphae

22
Q

Chlammydospores

A

Large, round, terminal cells with thick walls. They form by differentiation of the terminal cell of a hypha.

23
Q

Conidia

A

Resting/dispersal stage
Thick walled
Asexual spores

24
Q

Macrocondia

A

Large and contain multiple cells. Form by differentiation of a length of hypha. Have a septa between cells though

25
Q

Arthoconidia

A

Form by fragmentation of hyphae at septal planes. Alternate cells from thick walls. Later hyphae break apart at septa.

26
Q

Phiaoloconidia

A

Chains of Conidia bud from specialized terminal cells of hyphae

27
Q

What are the 5 different classifications of fungal infections? And what are they classified based off of?

A

Classified based off of location of infection.

Superficial
Cutaneous
Sub-cutaneous
Systemic
Primary pathogens vs. opportunistic
28
Q

Piedra

A

A type of superficial infection that attacks the hair.

29
Q

Tinea

A

A type of cutaneous infection of the skin.

  • lesion of inflamed rim of active infection and central clearing.
  • take the specimen from the rim of the infection!
  • usually found in soil, animals, and humans
30
Q

If patient has a superficial infection of the skin where should you take your sample?

A

The rim

31
Q

Subcutaneous mycoses

A

Fungi introduced by local trauma

32
Q

Three important genera of dermatophytes

A

EMT

Epidermophyton, microsporum, Tricophyton

33
Q

What is a common cause of subcutaneous infection?

A

Sporothrix schenkii - cigar shaped in tissue but hyphae conida in culture.

34
Q

Systemic mycoses

A

Endemic to specific areas
Infect all people, not just immonocomprimised people
Infection is usually in the lung but can spread
Exposure is often occupational so more frequent in males than females
Most infections are asymptomatic
Dimorphic - they are yeasts in 37 degrees but hyphae in standard culture at 30 degrees.

35
Q

How do you diagnose a fungal infection?

A 
Microscopy
Skin testing (similar to TB)
Serology
PCR
Culture
Exoantigen test
36
Q

Blastomyces dermatidis

A

Large yeast with broad-based buds.

Use a KOH mount to destroy everything other than the fungus, which has cell walls.

37
Q

Histoplasma capsulatum

A

Tuberculate conida in culture but tiny intracellular yeast in clinical material.

38
Q

Coccidioides immitis

A

Large spherules in the lung

39
Q

Paracoccidioides brazilienses

A

Yeasts with multiple buds. Looks like a ship wheel

40
Q

Candida albicans

A

Budding yeast, hyphae, pseudohyphae, microconidia, chlamydospores

  • borderline between true pathogen and opportunist
  • normal flora
  • causes vaginal infections, GI and skin infections in infants
  • causes oral infections (thrush)
  • forms “germ tubes” while other Candida’s don’t.
41
Q

Cryptococcus neoformans

A

Heavily-encapsulated yeast.

  • causes infections of the lung, which then go to the brain or meninges.
  • similar presentation as strep Neumo, H. Influenzae, N. Menigiditis
42
Q

Aspergillus

A 
Opportunist 
Especially in neutropenic patients
Can start in lung and then go to heart or great vessels
Use cytokines to treat
Ubiquitous in soil and plants
43
Q

Zygomyces - Nucor and rhizopus

A

Nasopharyngeal infections
Upper or lower respiratory tract disease
Tendency to branch at right angles
Can spread to brain

44
Q

Pneumocystis carinii

A

Usually infected in childhood
Rare causes of disease until the AIDS epidemic
Not possible to culture in clinical labs

Microbio Part 2 (14 decks)

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