Introduction to fungi Flashcards
What is a fungus?
A chemo-organotrophic eukaryote that lacks chlorophyll and forms spores.
Its cell wall contains polysaccharides, often chitin or glucan, and it absorbs nutrients.
Its membrane contains ergosterol as the major sterol.
What are the 3 main fungi groups?
basidiomycetes
ascomycetes
zygomycetes
How to tell difference between the 3 main fungi groups?
spores they form
basidiomycetes- basidium (basidiospores on top of structure)
ascomycetes- ascospores that are held within a sac called ascus
zygomycetes- rough walled zygote with one or more zygospores
What are dermatophytes?
fungi that grow on skin
use keratin as a source of nutrition
Names of dermatophyte infections?
called tinea….
capitis- scalp
facei- face
barbae- beard
corporis- skin
pedis-foot
unguium-toe nail bed
What is dermatophytosis?
Causative agents:
epidermophyton
microsporum
trichophytonspp
moulds with a predilection to degrade keratin as a nutrient source
What is pityriasus versicolor?
causative agents: malassezia spp
yeasts that also form hyphae in infected skin
What fungi and why are they relevant for patients in ICU?
Fungi are increasingly responsible for fatal diseases, acting as opportunistic pathogens of immunocompromised patients
Candida species infect deep organs of patients with various types of immune dysfunction, e.g. after abdominal surgery, burns, etc. (cases often in ICU)
Aspergillus spp. Infect deep organs of patients undergoing e.g. chemotherapy, stem cell transplantation
Why do fungi like to grow on human body?
favourable micro-environments (warm, moist areas) encourage growth of fungi on skin and mucous membranes
broad-spectrum antibacterial agents reduce competition for epithelial colonization sites in the gut
immunosuppression of all types may create a window of opportunity for fungal invasion
hyper immune response- inflammatory disease due to hyper immune response
Immunosuppression of host defences?
Iatrogenic: steroids
anti-cancer chemotherapy
solid-organ transplantation
Disease processes:
AIDS
leukaemia
endocrinopathies
Combinations of both
(higher risk of fungal infections)
What is the main species causing candida infections?
candida albicans
and candida galbrata- readily becomes resistant to anti gungal drugs
candida auris- found in ear and is resistant to three classes of antifungal drugs
What diseases do candida infections cause?
DEPENDS ON IMMUNE STATUS
oral
vaginal
skin
nail
oesophageal
urinary
vaginal
disseminated (life threatening)
What are candida spp?
yeast
but can switch shape to form hyphae (pleomorphic)
Describe candida in GI tract?
Within Gi tract candida is growing with other bacteria (part of commensal flora)
When patients in ICU given antibacterials, they will wipe out bacteria and yeast can overgrow.
Surgery or immunosupressive therapy and will injure GI tract, reducing lining and allowing yeast into blood stream.
Yeast also likes solid surfaces and so when finds a catheter - starts to grow as biofilm on catheter and is v drug resistant. Infected catheters with fungal biofilm .
What is aspergillosis and how is it formed?
Causative species:
Aspergillus fumigatus
Aspergillus flavus
Aspergillus nidulans (in CGD patients)
Aspergillus lentulus
other species on rare occasions
Types of disease:
simple asthma
asthma with eosinophilia
aspergilloma
invasive bronchopulmonary
aspergillosis
disseminated aspergillosis
Route of infection:
inhalation of conidia
