Intro to fungi Flashcards
classification of fungi
Kingdom: fungi
3 main groups within kingdom: Ascomycetes
Basidiomycetes
Zygomycetes
What is a fungus?
a chemo-organotrophic eukaryote that lacks chlorphyll and forms spores (like to get nutrients from environment)
informally what are the major types of fungi referred to as
moulds
mushrooms
yeast
What are fungi a significant cause of? examples
non-fatal diseases such as athlete’s foot, thrush
Fungi and fatal diseases
Candida species infect deep organs of patients with various types of immune dysfunction e.g after abdominal surgery, burns etc
aspergillus- infect deep organs of patients undergoing e.g chemotherapy and stem cell transplantation
What contribute to pathogenicity of fungal infections?
Host factors
favourable micro-environments (warm, moist areas) encourage growth of fungi on skin and mucus membranes
broad-spectrum antibacterial agents (antibiotics) can reduce competition for epithelial colonisation sites in the gut- they kill off some bacteria but others can be resistant- stay around.
immuno-suppresion of all types may create a window of opportunity for fungal invasion
What can cause immunosuppression of host defences?
Iatrogenic: steorids, anti-cancer chemo, solid- organ transplantation
disease processes: aids, leukaemia
or combo of both
diagnostic methods for detecting fungi
direct detection:- histophatology (the study of changes in tissues caused by disease), high-res CT scans
direct smear:- microscopy, staining etc
culture of fungus from normally sterile site- growth on selective medium
detection of circulating fungal antigens detection of circulating antibodies to fungi
PCR for fungal DNA
Problems with anti-fungal treatment
spectrum of activity static or cidal IV vs oral Toxicity costly resistance
What are antifungal medicines available as
topical- directly onto infection, gel, cream, ointment or spray
oral- capsule, tablet, liquid
IV
intravaginal anti-fungal pessaries- small soft tablets you can insert up the vagina
Common antifungal medicine names
clotrimazole
econazole
miconazole
Structure of a fungal cell
Nucleus Cell wall plasma membrane mitochondrion endoplasmic reticulum ribosome lipid inclusion- stored lipid droplets
Common types of fungal infection
ringworm- a skin infection athlete's foot- contagious fungal nail infection vaginal thrush some kinds of severe dandruff
Common types of local fungal infections
ringworm- a skin infection athlete's foot- contagious fungal nail infection vaginal thrush some kinds of severe dandruff
structure of fungi- a stylized mould mycelium
hypha
septa
clamp connection
What is mycelium?
mycelium is the vegetative part of a fungus- consisting of a mass of branching, thread-like hyphae
What is clamp connection on fungi?
a hook-like structure formed by growing hyphal cells of certain fungi
What is septa?
Septa divide hyphae. They have openings called pores between the cells, to allow the flow of cytoplasm and nutrients throughout the mycelium
What are hypha?
branching filaments making up mycelium of fungus
What are chains of conidia?
the asexual, non-motile spores that grow externally off a fungus. Borne from conidiophore- specialised hyphal branch.
Systemic fungal infections
Systemic mycoses are fungal infections affecting internal organs
What 2 main varieties of systemic fungal infection are there
endemic respiratory infections and opportunistic infections
Endemic infection
can cause systemic infection in people with normal immune function as well as those who are immune compromised Histoplasma capsulatum (causing histoplasmosis) a fungus found in the droppings of birds and bats in humid areas- fatal if spread throughout the body
Opportunistic infection
Fungi that only result in systemic infection in immuno-compromised or sick people
i.e those going through chemo, stem cell transplant, HIV patients
Dermatophytic fungal infection
most common fungal infections of the skin, hair, and nails
general properties of fungi
all fungi are eukaryotic
they have polysaccharides in their cell wall and ergosterol in cell membrane
non- motile due to rigid cell wall
they take up
dissolved organic compounds by osmosis for nutrition
Fungi are good at…
utilising any nutrients available to them
superficial diseases
skin, nails
biofilms can be formed on equipment such as
catheters
cryptococcal meningitis
1 million deaths/ year in Africa and Asia
fungi cell wall
cell wall of fungi is unique- have polysaccharides - (good targets for antifungal drugs)
How do fungi get obtain nutrients?
decompose dead organic matter
fungal cell reproduction
Fungi reproduce by budding:-
Mother cell produces a bud
when the bud becomes the same size as the mother size then a wall is formed between them and they then separate
- doubling time approx 2 hours (slower than bacteria)
dermatophytes cause what type of infection
- tinea
-they attack the skin
result in ringworm like infections - Like to digest keratin as nutrient source
Favourable conditions for fungal growth
warm temperatures (human body perfect) skin and mucus membranes
Candida allbicans
cause 40% of candida infections
oral infections
different cell shapes under microscope
important virulence factor:- fungal dimorphism?
ability to switch between hyphae (multicellular) and yeast (unicellular) cell
Ascomycetes
moulds and yeasts, some mushrooms
zygomycetes
moulds
basidiomycetes
mainly moulds and mushrooms, a few yeast
Systemic fungi:- candida
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, esophageal and many other forms of infections
