Introduction to Fungi Flashcards
Explain the classification and structure of Fungi.
Fungi can be assigned to one of three main divisions depending on biochemical data:
o Basidiomycetes - Mainly moulds and mushrooms, a few yeasts. Have basidia underneath the cup of the mushroom.
o Ascomycetes - Moulds and yeasts, some mushrooms
o Zygomycetes - Moulds
They act as opportunistic pathogens that tend to infect immunocompromised patients.
Describe the clinically important systemic and dermatophytic fungal infections.
o Dermatophytes
These fungi have a predilection to digesting keratin as a nutrient source, and so tend to attack skin and result in ringworm like infections.
E.g. Pityriasis Versicolor – Yeasts that form hyphae in infected skin.
o Systemic fungi
Candida is a species of fungi commensal to the GI tract, but one which can cause a lot of problems. They are yeasts and responsible for oral, vaginal, skin, nail oesophageal and many other forms of infections.
What is a fungus?
- Any member of the group of eukaryotic organisms that includes unicellular microorganisms such as yeasts and molds, as well as multicellular fungi that produce familiar fruiting forms known as mushrooms.
- A characteristic that places fungi in a different kingdom from plants, bacteria and some protists, is chitin in their cell walls.
- Fungi are heterotrophs; they acquire their food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment.
- Fungi do not photosynthesise.
- Growth is their means of mobility, except for spores (a few of which are flagellated), which may travel through the air or water. Fungi are the principal decomposers in ecological systems.
Describe some diagnostic methods used in medical mycology
o Direct detection (Histopathology, high-res CT scans)
o Detection of circulating fungal antigens
o Detection of circulating Abs to fungi
o PCR for fungal DNA
o Culture of fungus from normally sterile site
What are the three main groups of anti-fungal agents?
Polyenes
Azoles
Echinocandins
What are the issues surrounding current anti-fungal agents?
Very few available
Increasing resistance
Poor spectrum of activity
Effect of cidal vs static drugs
Describe the differences between cidal and static drugs
- Static antibiotics – prevents organisms from multiplying and relies on immune system to clear up infection
- Cidal antibiotics – kills organisms without help of immune system
What are the three groups of the fungal kingdom?
Basidiomycetes - mushrooms and mould
Ascomycetes - yeast and mould
Zygomycetes - bread moulds
What are the sexual spores of each group in the fungal kingdom?
Basidiomycetes - basidiospore
Ascomycetes - ascospore
Zygomycetes - zygospore
What are the asexual spores of each group in the fungal kingdom?
Basidiomycetes - conidium
Ascomycetes - conidium
Zygomycetes - sporangiospores
What fungal group does Candida and aspergillus species belong to?
Ascomycetes
What fungal group does Cryptococcus species belong to?
Basidiomycetes
What fungal group does Rhizopus species belong to?
Zygomycetes
