Fungal Infections and Antifungals

Question 1

What types of fungi are there? Name some examples of these.

Answer 1

Yeast and moulds

Yeasts:

• Candida
• Cryptococcus

Moulds:

• Aspergillus
• Dermatophytes
• Mucormyocosis

Some species are dimorphic, transitioning between yeasts and moulds depending on the environment.

Question 2

Describe candida infection, and its treatment.

Answer 2

Usually in the mouth or perineum, commonly affecting people after antibiotics treatment or steroid treatment. The most common species is C. albicans.

In the immunocompromised, it can progress to spleen or liver, or even the eyes and arteries.

Diagnosis:

• Culture and antibodies
• Imaging if indicated

Treatment:

• Fluconazole (Amphotericin B for invasive disease)
• Echinocandin

Question 3

Describe Cryptococcus infection and its treatment

Answer 3

Usually in those who are susceptible:

• T cell immunocompromise
• HIV
• Post transplant

Disseminates to the CNS, and is the second most common cause of death in AIDS. There are variants which can cause meningitis in the immunocompetent.

Diagnosis:

• Cryptococcal antigen
• India ink stain

Treatment:

• Amphotericin B for 3 weeks
• +/- flucytosine

Question 4

Describe aspergillus infection and its treatment.

Answer 4

This can cause thing:

1) Mycotoxicosis
2) Allergic bronchopulmonary disease (common)
3) Colonisation without invasion (post-TB)
4) Necrotising, granulomatous, invasive disease
5) Disseminated and systemic disease

Diagnosis:

• On microscopy
• ELISA and PCR

Treatment:

• With voriconazole for 6 weeks
• Amphotericin B

Question 5

Describe dermatophyte infection and its treatment

Answer 5

This is a more superficial disease

Tinea (e.g. Tricophyton)

• Ringworm
• Tinea pedis
• Tinea capitis

Pityriasis (Malassezia)

• Seborrhoeic dermatitis
• Versicolour

Question 6

Describe mucormyosis infection and its treatment

Answer 6

In the immunocompromised and it can be very disabling. Presents with cellulitis with black discharge, and can cause serious ophthalmoplegia.

Treated:

• Surgical debridement
• This is a surgical emergency

Question 7

What are the types of antifungals

Answer 7

They depend on their target:

• Cell membrane synthesis
• DNA synthesis
• Cell wall synthesis

Question 8

Describe the target of cell membrane synthesis and give examples. Give side effects or precautions of these drugs.

Answer 8

The fungal cell membrane uses ergosterol and not cholesterol so can be targeted. Examples include:

Polyenes:
- Amphotericin B
Azoles:
- Fluconazole
- Ketoconazole

Precautions:

• Azoles: P450 inducers so beware of interactions
• Polyenes: toxic so sometimes wrapped in liposomes
• Both: check blood levels to ensure good dose

Question 9

Describe the target of DNA synthesis and give examples. Give side effects or precautions of these drugs.

Answer 9

These disrupt the DNA/RNA synthesis of fungal infections. Examples include:

Flucytosine

This is no longer used much, and is now mainly used in combination therapy for Cryptococcus.

SE: diarrhoea, blood disorders
Precautions: measure blood levels

Question 10

Describe the target of cell wall synthesis and give examples. Give side effects or precautions of these drugs.

Answer 10

Fungi have a cell wall whereas as mammalian cells do not. Examples include:

Echinocandins

• Caspofungin
• Micafungin
• Anidulafungin

Precautions:
These have no activity against Cryptococcus so check the sample is sensitive before prescribing