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Year 5 - Pathology ICSM1 > Microbiology 16 - Fungal infections > Flashcards

Microbiology 16 - Fungal infections Flashcards

1
Q

What is the main conponent of fungal cell walls?

A

Chitin

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2
Q

What is the main component of fungal cell membranes?

A

Ergosterol

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3
Q

What is the reproductive method of yeats?

A

Budding

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4
Q

Recall 3 examples of yeasts that are clinically important

A

Candida
Cryptococcus
Histoplasma

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5
Q

What are moulds?

A

Multicellular hyphae

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6
Q

Give 2 examples of moulds that are clinically important

A

Dermatophytes

Aspergillus

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7
Q

Recall the empiric treatment for oral, vulvovaginal and cutaneous candida infection

A

Oral candidiasis: nystatin suspension/fluconazole
Vulvovaginal and cutaneous: fluconazole/clotrimazole pessary if oral not tolerated/topical imidazole

Advise patient that topical treatments like imidazole may damage latex condoms/diaphragms

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8
Q

Recall the principles of candidaemia management

A
  1. Look for source and signs of dissemination:
    - Imaging
    - Serology for beta-D-glucan
    - echocardiogram/fundoscopy (candida is sticky- likes to stick to surfaces)
  2. Antifungals for at least 2/52 from date of first negative blood culture - repeat BCs every 48 hours

Grown on Sabouraud agar

If there are any central lines/catheters remove them

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9
Q

Recall the different types of cryptococcus, and which of these infect immunocompetent vs immunocompromised hosts

A

Serotypes A and D = cryptococcus neoformans (immunocompromised hosts)

Serotypes B and C = cryptococcus gatti (immunocompetent hosts)

Cryptococcus can cause pulmonary infection and meningitis

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10
Q

Which type of cryptococcus can cause meningitis?

A

Cryptococcus gatti (serotype B/C-immunoCompetent hosts)

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11
Q

What ink can be used to stain for cryptococcus?

A

India Ink

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12
Q

How should cryptococcus infection be managed?

A
  1. Induction: 2/52 of amphotericin B + flucytosine
  2. Consolidation: 8/52 of high dose fluconazole
  3. Maintenance: 1 year low-dose fluconazole

Resistant to echinocandins

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13
Q

Which type of aspergillus disease is an allergic disease?

A

Allergic Bronchopulmonary Aspergillosis (ABPA)

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14
Q

How does aspergillus appear under the microscope?

A

Fluffy colonies

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15
Q

What parts of the body can be infected by aspergillus?

A

Pre-formed cavities (eg. by TB) - so treated pulmonary TB may be in the history

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16
Q

What is a galactomannan assay used for?

A

Aspergillosis diagnosis

17
Q

Why is pneumocystis jirovecii an unusual fungus?

A

No ergosterol wall

18
Q

What is the typical history for PCP pneumonia?

A

Desaturating on exertion

Walking 10m and feeling breathless

19
Q

What are the clinical features of mycormycoses?

A

Orbital/facial cellulitis with discharge of black pus from nose/ palate

Typically only affects immunocompromised/diabetics

20
Q

How are mycormycoses managed?

A

Surgical management-very invasive disease
Early referral to ENT
Strong dose of ambisone (amphotericin B)- MOA- polyene-target cell membrane

Caused by moulds starting with “rhizo… smth”

21
Q

Recall an example of a dermatophyte

A

tinea

22
Q

Where does tinea cruris infect?

A

Groin

23
Q

How is tinea diagnosed?

A

Often clinically, but can be confirmed via skin scrapings for MC&S

24
Q

Recall 4 classes of antifungal medications

A

Polyenes- Amphotericin B (Ambisone)- cell membrane- Nephrotoxic
Azoles- Fluconazole, Clotrimazole- cell membrane- Abnormal LFTs
Echinocandins- Caspofungin- cell wall- no side effects
Pyrimidine analogues- flucytosine- DNA/RNA synthesis- Blood disorders

25
Q

Recall the side effect profile of each class of antifungal

A

Azoles - abnormal LFTs
PolyeNes - Nephrotoxicity
Echinocandins - relatively innocuous
Pyrimidine analogues - blood disorders

26
Q

What is the mechanism of action of azoles?

A

Inhibit ergosterol synthesis

27
Q

What is the mechanism of action of polyenes?

A

Bind sterols in membranes to create leakage of electrolytes

E.g Amphotericin B/Ambisome

28
Q

Give 2 examples of polyene medications

A

Amphotericin B

Nystatin

29
Q

Which 2 types of fungus are echinocandins particularly useful for?

A

Candida
Aspergillus

NOT useful for cryptococcus

Examples: Micafungin, Caspofungin

30
Q

What class of antifungal is flucytosine?

A

Pyrimidine analogue

31
Q

What antifungal is cryptococcus resistant to?

A

Echinocandins (E.g- Caspofungin-affects cell wall)

Echinocandins are useful for candida/aspergillus

32
Q

What is a pathognomonic sign seen on microscopy of Candida albicans to differentiate it from the other candida species

A

Germ tubes

33
Q

How to identify the different aspergillus species?

A

Cannot tell based on hyphae, have to look at spores.

34
Q

Treatment of aspergillosis?

A

At least 6weeks of amphotericin

Year 5 - Pathology ICSM1 (85 decks)

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