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MICBI Fungi and Parasites > L13 Basic mycology > Flashcards

L13 Basic mycology Flashcards

1
Q

Fungi are eukaryotic. Describe the content of fungal cell walls?

A

Contains glycans: mannan, glucan, chitin

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2
Q

Fungal cell membranes are phospholipid bilayers with ergosterols. Therefore, ________, _____ such as _______ can be used as treatment?

A

Azole, polyene

e.g. amphotericin B

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3
Q

What are the differences between yeast and mould, which are both fungi?

A

Yeast: unicellular with pseudohyphae
Mould: multicellular with true hyphae = germ tubes

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4
Q

Candida albicans are a type of __________ fungi which changes with the environment - Room temperature: yeast; 37 degrees: mould.

A

Dimorphic

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5
Q

Fungi like Malassezia furfur, dermatophytes and Candida species stain with ______ wet mount, which is used to ________________. It also stains with lactophenol cotton blue as counterstain to highlight the filaments.

A

KOH; digest the keratin on skin (digest cell junction)

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6
Q

Fungi can be cultured in _________ agar.

A 
Sabouraud agar (dextrose 4%)
(sugar lover)
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7
Q

This fungi is Gram stain + (stained blue-black) with budding yeast and psedohyphae at 20 degrees celcius. It is also oval in shape. Name the fungi and how is it diagnosed?

A

Candida albicans.

  • Diagnosed by KOH wet mount
  • Germ tube +ve test: formation of true hyphae (germ tube) in hourse serum, 37 degrees celcius for 2h
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8
Q

Name the 4 types of Candida non-albicans. What would be the expected results when they are put to the germ tube test? What does it suggest?

A
  1. C. glabrata. [bra]
  2. C. krusei. [cruise]
  3. C. parapsilosis [para-絲綢]
  4. C. tropicalis [go to tropical area]
  • Germ tube -ve; anti-fungal susceptibility
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9
Q

Name the 3 clinical diseases that Candida albicans can cause.

A
  1. Oral candidiasis - inhaled steroid users
  2. Candida oesophagitis - AIDS defining illness (CD4 <100)
  3. Candida vulvovaginitis
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10
Q

What is the infection site of Candida albicans?

A

Systemic

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11
Q

Which of the following about pneumocystis jirovecii is incorrect? Explain.
A. It is a yeast
B. It appears in clusters
C. They are cup-shaped, collapsed basketball like
D. It is diagnosed by India ink in CSF
E. Pneumocystis carinii is the form in rats
F. It appears in small amounts

A

D

  • This is Cryptococcus neoformans species complex!
  • Diagnosed by Bronchoalveolar lavage (BAL)/ induced sputuum - Toluidine blue O stain.

F: microscopy: >5/HPF (high power field)

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12
Q

Pneumocystis jirovecii transmission?

Disease that it may cause?

A
  • By inhalation

- Pneumocustic pneumonia in severe immunocompromised, e.g. AIDS (CD4 <200)

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13
Q

Pneumocystis jirovecii is an obligate extracellular yeast. How is it cultured?

A

Non-cultivable!

only in-vivo!

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14
Q

This fungi is a yeast that has a large capsule that is as thick as its cell diameter. It is also anti-phagocytic. Name the fungi.

A

Cryptococcus neoformans species complex

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15
Q

For the Cryptococcus variant neoformans,

  1. Serotype?
  2. Where can it be found?
  3. Affect what patients?
A

Serotype A/D
Pigeon faeces, soil
immunocompromised (e.g. AIDS)

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16
Q
  1. What is the other variant other than Cryptococcus variant neoformans?
  2. Serotype?
    It is found in eucaluptus tree, affects immunocompromised.
  3. Prognosis?
A

Cryptocccus variant gattii
Serotype B/C
Poor prognosis

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17
Q

How are Cryptococcus neoformans species complex diagnosed? Why it can be diagnosed by this way?

A

Method 1:

  • CSF: India ink (negative stain, budding yeasts with capsular halo)
  • It is because it causes meningoencephalitis due to neurotropism of the fungi

Method 2:
*Latex partical agglutination of Cryptococcal capsular polysaccharides

18
Q

How is Cryptococcus neoformans species complex transmitted? Other than meningoencephalitis, what rare diease it cause?

A

Inhaltion;

Extra-neural disease: pneumonia, prostate infection

19
Q

____________ is a dimorphic fungi that is lipid dependent. It is present in normal skin flora.

A

Malassezia furfur

20
Q

How can Malassezia furfur be diagnosed?

A

Skin scrappings:

  • KOH wet mount (fungal filaments)
  • culture with olive oil supplements
21
Q

What is the disease caused by Malassezia furfur?

A

Tinea versicolor

(hyper-/hypo-pigmentation of the skin)

22
Q

What is the microbiological name for the Bread mould? Give examples of its species.

A

Zygomycetes

  • Rhizomucor
  • Mucor
  • Rhizopus
23
Q

What distinguishable features can be seen in Zygomycytes?

A
  1. Irregular
  2. Non-septated hyphae
  3. with Right-angle branching
24
Q

Name 3 fungi that you have learnt that causes cutaneous infection.

A
  1. Malassezia furfur
  2. Zygomycetes
  3. Dermatophytes
25
Q

Which of the following about Zygomycetes are correct?
A. They are fragile thus difficult to culture
B. Diagnosis is by molecular study or seroglogy
C. It affects DM patients
D. It affects patients with transplant
E. Its infection has a low mortality rate

A

All except E
high mortality

C and D are both correct: immunocompromised (HIV too)

26
Q

__________ is a mould whose infection is restructed to the keratin layer of the skin but not further.

A

Dermatophytes

27
Q

Skin scrappings/ Nail clipping for KOH and culture can be used to diagnose Dermtophytes.
List, for different species, whether Microconidia/ Macroconidia are present ot not. (reproductive organs)

A
  1. Microsporum species
    - have microconidia
    - fusiform, thick-walled macroconidia
  2. Trichophyton species
    - have microconidia
    - rare macroconidia
  3. Epidermophyton spcies
    - absent microconidia
    - thin-walled macroconidia
28
Q

Name the 3 different Dermatophytes species you have learnt.

A
  1. Microsporum species
  2. Trichophyton species
  3. Epidermophyton spcies
29
Q

What is the disease caused by Dermatophytes? Briefly discribe the disease. (2)
List the possible manefistations (5).

A

Tinea infection : ring-like pruritic skin lesions

  1. Tinea capitis (scalp)
  2. Tinea corporis (body)
  3. Tinea crutis (groin)
  4. Tinea pedis (foot)
  5. Onychomycosis (nails)
30
Q

_______________ (1) is a yeast/mould/dimorphic fungi (1) that is associated with rose thorns, traumatic inplantations.

A

Sporothrix schenckii

- dimorphic fungi

31
Q

List all the dimorphic fungi that you have learnt.

A
  1. Candida albicans
  2. Malassezia furfur
  3. Sporothrix schenckii
  4. Talaromyces (penicillium) marneffei
32
Q

Sporothrix schenckii causes what disease? Explain what structure of the body is involved(2)

A

Sporotrichosis/ Rose Gardener disease: Lymphangitis with lymphocutaneous spread

33
Q

Aspergillus fumigatus is a yeast/ mould/ dimorphic fungi (1) with what distinguishing features? (3)

A 
- Mould
Features
1. Septated hyphae (vs. Zygomycetes) 
2. Acute angle branching 
3. Conidia
34
Q

Which of the following abour Aspergillus fumigatus are correct?
A. It can be diagnosed by fungus ball in the lung on CXR
B. It can be diagnosed by KOH wet mount by biopsy
C. It can be diagnosed by checking the IgE level for ABPA (Allergic bronchopulmonary aspergillosis)
D. It can be cultured with top smoky grey-green with conidia and bottom yellow in sabouraud agar

A

All of the above

35
Q

What diseases can Aspergillus fumigatus cause? (4)

A
  1. Allergic reactions (ABPA (Allergic bronchopulmonary aspergillosis))
  2. Aspergilloma
  3. Angioinvasive aspergillosis
  4. A. flavus produces aflatoxin that causes HCC
36
Q

A patient with soil exposure, Chinese, presented with skin infection. Morphology shows diffusible red-wine color pigment on agar. Name the fungi.

A

Talaromyces (penicillium) marneffei

紅酒 罵你肥

37
Q

Which of the following is false about Talaromyces (penicillium) marneffei?
A. It is a mould
B. It is endemic in SE Asia
C. It is potentially lethal as it causes sytemic infection
D. Inhalation of its conidia may cause the disease

A

A

It is a dimorphic fungi

38
Q

Other than Talaromyces (penicillium) marneffei, Name 2 other geographical mycosis which are in Soutern part of North America.

A
  1. Histoplasmosis capsulatum (gray) - with large, round macroconidia
  2. Coccidioides immitis (black) - with spherules (all daughter cells inside)
39
Q

Name the fungi: collapsed basketball-like cysts.

A

Pneumocystis jirovecii

40
Q

Name the fungi: India ink

A

Cryptococcus neoformans

41
Q

Name the fungi: Sepated hyphae with acute angle branching.

A

Aspergillus fumigatus

MICBI Fungi and Parasites (3 decks)

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