Fungi Flashcards
What are common fungal infection?
Cryptococcus neoformans
Candida infections - oral/vaginal/systemic
Aspergillus fumigatus
Superficial infection (dermatophyte/nail)
What are fungi? (function)
FUNCTION: chemo-organotrophic eukaryote that lacks chlorophyll and forms spores.
What are fungi (structure)?
STRUCTURE: cell wall contains polysaccharides, often chitin and cellulose and it absorbs nutrients. Its major membrane contains ergosterol as the major sterol.
Sterol = type of lipid, subgroup of steroids
Groupings of Candida species problem
Grouped by morphology NOT genetic relatedness
Why? For clinical identification
Problem: identifying to Genus is not enough, resistance varies greatly between
Fungal Kingdom (groups)
Basidiomycetes
Ascomycetes
Zygomycetes
Main, high mortality fungal infections of immunocompromised
Candida spp. Infect deep organs of patients with various types of immune dysfunction
Aspergillus spp. Infect deep organs of patients undergoing e.g. chemotherapy, stem cell transplantation
Crypotcoccus spp. - moves from lungs to nervous system
What is Aspergillus fumigatus?
Farmers’ lung
Of the larger groups, which one do Cryptococcus spp. belong to?
Basidiomycetes
Example of an Ascomycetes fungi
Candida spp., Aspergillus spp., Neurospora
Example of a Zygomycetes fungi
Rhizopus species, bread moulds
Cause of athlete’s foot
Epidermophyton
Cause of thrush
Candida spp.
Cause of a lot of skin conditions (inc. dandruff)
Malassezia spp.
Classes of antifungals
polyenes
azoles
echinocandins
What is a cause of dermatophyte infections?
tinea - use keratin as a food source
Outline Chronic mucocutaneous
candidiasis (CMC)
can arise in individuals with an unusual combination of endocrine and immune dysfunction (autoimmune polyendocrinopathycandidiasis -ectodermal dystrophy — APECED)
- more vulnerable to fungal infections
Main causative species of Candida infections
C. albicans C. tropicalis C. glabrata C. krusei C. parapsilosis
What sort of infections do Candida spp. cause?
oral/vaginal/skin/nail/oesophageal/urinary/disseminated
Main causative species of Aspergillus infections
A. fumigatus
A. flavus
What sort of infections do Aspergillus spp. cause?
simple asthma asthma with eosinophilia aspergilloma invasive - bronchopulmonary/aspergillosis disseminated aspergillosis
What is are aspergillus infections mainly associated with?
haematological
malignancies
Main causative species of Cryptococcus spp. infections
Cryptococcus neoformans
C. gattii
What sort of infections do Cryptococcus spp. cause?
pulmonary cryptococcosis
meningitis
disseminated infection
Examples of Azoles
Fluconazole
Voriconazole
Posaconazole
How do Azoles work?
Target ergosterol (cell wall) Make ergosterol into a toxic sterol
Example of a Polyene
Amphotericin B
How do Polyenes work?
Target membrane
Binds to ergosterol, makes pore in membrane
Example of an Echinocandin
Caspofungin
How do Echinocandins work?
Target cell wall
Causes cell wall stress by blocking 1,3 beta glucan synthase
Types of Cryptococcus spp. that cause disease
Cryptococcus neoformans
Cryptococcus gattii (complex of C. bacillisporus and C tetragattii)
What is special about Cryptococcus gattii?
Can target non-immunosuppressed people
Fungal pathogens in immunosuppressed - unattributed
Rhizopus arrihizus
Exophiala
Non-fatal fungal infection examples
Athlete’s foot - Epidermophton, Microsporum and Trichophyton spp.
Thrush - Candida spp.
pityriasis versicolor - Malassezia spp.
Dermatophyte infections - tinea (keratin feeding)
What is the significance of GXM and GXMGal?
Forms Capsule around Cryptococcus- major role in virulence
What is the significance of titan cells?
Higher virulence
- found more in Cryptococcus gattii (tetragattii)
- also protection when inside macrophage
Interesting feature of Cryptococcus when taken in by macrophage
vomocytosis
- makes the macrophage release it
