Fungal infections and antifungals Flashcards
Give two reasons why fungal infections can be difficult to diagnose
- Slow growing
- Can be masked by bacteria
Give two ways of classifying fungal infections
Yeast vs mould (description based on appearance)
Superficial vs deep (based on site of infection)
What are dimorphic fungal infections?
Can exist as both mould and yeast form, often due to temperature. Therefore usually yeast during infection but mould at room temp (ie in lab)
“Mould in the Cold, Yeast in the Beast”
Give 3 common sites of superficial fungal infection
Skin, hair, nails
How are superficial fungal infections diagnosed?
Woods lamp (UVA/black light)
Name two types of organism that cause superficial fungal infection.
Dermatophytes
Malassezia
Which organisms cause tinea infections? Give a specific example
Dermatophytes, eg Tricophyton rubrum
Which organisms cause fungal pityriasis infections? Give a specific example
Malassezia globosa/furfur
Give 3 examples of tinea infection
Ringworm
Athlete’s foot
Jock itch
Give 2 examples of fungal pityriasis infection
Seborrhoeic dermatitis
Pityriasis/Tinea versicolour
Name 3 fungal infections that can become deep-seated, especially in the immunocompromised
Candida
Aspergillus
Cryptococcus
How are deep candida infections diagnosed?
Culture
Mannan antigen test
(Mannan is a glycoprotein found in the cell walls of Candida albicans)
Antibody tests
How do Aspergillus infections present?
Can be anywhere on spectrum from allerfy to invasion.
In immunocompromised presents as pneumonia. High mortality
How is aspergillus diagnosed?
ELISA
PCR
Beta-glucan test
How does cryptococcus infection present in the immunocompromised (particularly HIV)?
Meningitis with insidious onset
How is cryptococcus diagnosed?
Cryptococcal antigen in serum/CSF
List the 5 classes of antifungal
Polyene Azole Terbinafine Flucytosine Echinocandin
Give an example of a polyene antfiungal
Amphotericin
Give an example of an azole antifungal
Fluconazole
Give an example of an echinocandin
Caspofungin
Describe the target of polyene antifungals
Cell membrane integrity
Describe the target of azole antifungals
Cell membrane synthesis
Describe the target of terbinafine antifungals
Cell membrane permeability, leading to cell lysis
Describe the target of flucytosine antifungals
DNA synthesis
Describe the target of echinocandin antifungals
Cell wall
Which classes of antifungals are indicated for yeast infections?
Polyenes, Azoles and Echinocandins
What is an advantage of echinocandins?
Less toxic side effects than other anti-yeast antifungals
Which class of antifungals is indicated for dermatophytic mould infections (tinea)?
Terbinafine
What is the antifungal Amphotericin B used to treat? (specific infection)
Cryptococcal meningitis + invasive fungal infection
