Anti-Fungal Agents

Question 1

What are dermatophytes? [1]

Answer 1

a fungi that doesn’t colonise “live tissue” but they do colonise keratinised tissue and cause common infections of the hair, skin and nails

Question 2

Name 3 systemic fungal infections that only affect the immunocompromised and state the causative microbe for each infection [6]

Answer 2

1. Fungal meningitis
   
   • by cryptococcus neoformans
2. Aspergillosis in the lungs
   
   • by aspergillus fumigatus
3. Pneumocystis pneumonia
   
   • by pneumocystis jiroveci

Question 3

What does cryptococcus neoformans cause and what condition is it often secondary to? [3]

Answer 3

1. Causes cryptococcosis of the lungs and meningitis
2. Often secondary to a HIV infection

Question 4

What 3 conditions does aspergillus fumigatus cause? [3]

Answer 4

1. Allergic bronchopulmonary aspergillosis (ABPA)
2. Invasive pulmonary aspergillosis (IPA)
3. Aspergilloma

Question 5

Allergic bronchopulmonary aspergillosis (ABPA):

1. what is it? [1]
2. what conditions is it associated with? [2]
3. how do you treat it? [1]

Answer 5

1. Allergic reaction to the fungal infection
2. Associated with:
   
   • cystic fibrosis (CF)
   • asthma
3. Give prednisone (antiallergic agent)

Question 6

Invasive pulmonary aspergillosis (IPA):

1. spread? [1]
2. who gets it? [1]
3. treatment? [2]

Answer 6

1. Becomes systemic and spreads throughout the body
2. Common in immunocompromised
3. Treat with voriconazole and amphotericin B

Question 7

Aspergilloma:

1. what is it? [2]
2. treatment? [2]

Answer 7

1. Fungal ball that develops in an area of past lung disease or lung scarring — e.g. TB or lung abscess
2. No treatment unless bleeding - surgery

Question 8

Pneumocystis jiroveci:

1. who gets it? [1]
2. presentation? [5]
3. treatment and prophylaxis? [2]

Answer 8

1. Only affects immunocompromised
2. Causes pneumonia:
   
   • fever,
   • cough
   • SOB,
   • rapid breathing
3. Treatment and prophylaxis
   
   • trimethoprim
   • sulfamethoxazole

Question 9

Describe the mechanism of action of antifungal drugs ending in -azole (such as Miconazole, Ketoconazole, Clotrimazole etc.) [2]

Answer 9

enzyme inhibitor: they inhibit 14-methylsterol alpha-demethylase which produce ergosterol which is an essential component of the fungal plasma membrane (equivalent of cholesterol in our cell membranes), leading to cell death

Question 10

How do amphotericin B drugs work? [3]

Answer 10

1. They also antifungals that target the ergosterol (IS NOT AN ENZYME INHIBITOR)
2. It’s a large molecule with a hydrophobic and hydrophilic side
   
   • binds to ergosterol
     
     • break membrane by forming pores in the fungal membranes
       
       • leading to cell death