Introduction to fungi Flashcards
what is a fungus?
chemo-organic eukaryote that lacks chlorophyll and forms spores.
what does the cell wall of a fungus contain?
polysaccharides, often chitin or cellulose
what is the major sterol of the fungal membrane?
ergosterol
what is the mycelium?
the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae
what are the three groups of fungi?
basidiomycetes
ascomycetes
zygomycetes
what is the difference between the asexual spores of basidio and ascomycetes and zygomycetes?
zygomycetes asexual spore is sporangiospore as opposed to conidium
what is the structure of a basidiomycete?
basidiospores sit on top of the basidium, which is attached to the hypha
what is the structure of an ascomycete?
ascospores contained within a sac (ascus)
what is the structure of zygomycetes?
a rough walled zygote contains one or more zygospores
what are yeasts?
fungi that favour a unicellular habit
what diseases are caused by dermatophytes?
"ringworm" or TINEA: capitis facei barbae corporis cruris manum pedis unguium
when would conidiophore be released?
when nutrients are low and the fungi needs to try and sporulate (spread)
what are some causative agents of dermatophytosis (tinea)
epidermophyton microsporum and trichophyton spp
what is a causative agent of pityriasis versicolor?
malassezia spp., which are yeasts that also form hyphae in infected skin
when would a candida infection be fatal?
in immunocompromised patients where it can affect the deep organs.
what host factors can increase pathogenicity of fungal infections?
favourable (warm, moist) micro environments
broad spectrum antibacterial agents can reduce competition for epithelial colonisation sites in the gut
any immunosuppression
what different ways can a host become immunocompromised?
iatrogenic
disease processes
combinations of the above
what are some examples of iatrogenic immunosuppression?
steroid
anti cancer chemo
solid organ transplantation
what are some disease processes causing immunocompromisation?
AIDS
leukaemia
endocrinopathies
what are risk factors for candidiasis?
age, antibiotic therapy, endocrine disorders, immune defects, immune suppression, surgery
what is the most common type of candida species causing infection?
candida albicans
are candida yeasts?
Yes
can candida form hyphae?
Yes
what would cause a chronic mucocutaneous infection?
genetic defects
and endocrine defects and immune defects
what are the main causative species of aspergillosis?
aspergillus fumigatus
what diseases can aspergillosis cause?
asthma
aspergilloma
asthma ith eosinophilia
what type of fungus is apergillus?
mould
how does aspergillosis infection occur?
inhalation of conidia
what is a contributing factor to developing invasive pulmonary aspergillosis?
haematological malignancy
what is the main causative species of cryptococcosis?
cryptococcus neoformans
what diseases are caused by cryptococcus spp.
pulmonary cryptococcosis
meningitis (particularly in AIDS patients)
what are some diagnostic methods of detecting fungal infections?
histpathology
high-res CT scans
direct smear
detection of circulating fungal antigens
detection of circulating antibodies to fungi
PCR for fungal DNA
culture of fungus from normally sterile sites
how can dermatophytes be visualized?
directly in skin scales
what are some different classes of antifungal drugs?
triazoles and allylamines
echinocandins
polyenes
flucytosine
what do triazoles and allylamines target?
sterols
what do echinocandins target?
target cell wall
what do polyenes target?
target the fungal cell membrane
what does flucytosine target?
targets DNA synthesis
what are some examples of polyenes?
amphotericin B
Nyastatin
what are some examples of azoles?
clotrimazole
fluconazole
miconazole
what are some examples of echinocandins?
anidulafungin
caspofungin
micafungin (IV)
what are some problems with antigfungals?
spectrum of activity of the drug IV vs oral toxicity resistance cost static or cidal
