Microbiology 16 - Fungal infections

Question 1

What is the main conponent of fungal cell walls?

Answer 1

Chitin

Question 2

What is the main component of fungal cell membranes?

Answer 2

Ergosterol

Question 3

What is the reproductive method of yeats?

Answer 3

Budding

Question 4

Recall 3 examples of yeasts that are clinically important

Answer 4

Candida
Cryptococcus
Histoplasma

Question 5

What are moulds?

Answer 5

Multicellular hyphae

Question 6

Give 2 examples of moulds that are clinically important

Answer 6

Dermatophytes

Aspergillus

Question 7

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

Answer 7

Oral: nystatin

Vulvovaginal and cutaneous: co-trimoxazole, but if oral treatment is needed then use fluconazole

Question 8

Recall the principles of candidaemia management

Answer 8

1. Look for source and signs of dissemination:
   - Imaging
   - Serology for B-D-glucan
   - echo/fundoscopy
2. Antifungals for at least 2/52 from date of first negative blood culture - repeat BCs every 48 hours

Question 9

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

Answer 9

Serotypes A and D = cryptococcus neoformans (immunocompromised hosts)

Serotypes B and C = cryptococcus gatti (immunocompetent hosts)

Question 10

Which type of cryptococcus can cause meningitis?

Answer 10

Cryptococcus gatti

Question 11

What ink can be used to stain for cryptococcus?

Answer 11

India Ink

Question 12

How should cryptococcus infection be managed?

Answer 12

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

Question 13

Which type of aspergillus disease is an allergic disease?

Answer 13

ABPA

Question 14

How does aspergillus appear under the microscope?

Answer 14

Fluffy colonies

Question 15

What parts of the body can be infected by aspergillus?

Answer 15

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

Question 16

What is a galactomannan assay used for?

Answer 16

Aspergillosis diagnosis

Question 17

Why is pneumocystis jirovecii an unusual fungus?

Answer 17

No ergosterol wall

Question 18

What is the typical history for PCP pneumonia?

Answer 18

Desaturating on exertion

Question 19

What are the clinical features of mycormycoses?

Answer 19

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

Question 20

How are mycormycoses managed?

Answer 20

LONG duration of ambisone (amphotericin B)

Question 21

Recall an example of a dermatophyte

Answer 21

tinea

Question 22

Where does tinea cruris infect?

Answer 22

Groin

Question 23

How is tinea diagnosed?

Answer 23

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

Question 24

Recall 4 classes of antifungal

Answer 24

Azoles
Polyenes
Echinocandins
Pyrimidine analogues

Question 25

Recall the side effect profile of each class of antifungal

Answer 25

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

Question 26

What is the mechanism of action of azoles?

Answer 26

Inhibit ergosterol synthesis

Question 27

What is the mechanism of action of polyenes?

Answer 27

Bind sterols in membranes to create leakage of electrolytes

Question 28

Give 2 examples of polyene medications

Answer 28

Amphotericin B

Nystatin

Question 29

Which 2 types of fungus are echinocandins particularly useful for?

Answer 29

Candida

Aspergillus

Question 30

What class of antifungal is flucytosine?

Answer 30

Pyrimidine analogue