Introduction to fungi

Question 1

what is a fungus?

Answer 1

chemo-organic eukaryote that lacks chlorophyll and forms spores.

Question 2

what does the cell wall of a fungus contain?

Answer 2

polysaccharides, often chitin or cellulose

Question 3

what is the major sterol of the fungal membrane?

Answer 3

ergosterol

Question 4

what is the mycelium?

Answer 4

the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae

Question 5

what are the three groups of fungi?

Answer 5

basidiomycetes
ascomycetes
zygomycetes

Question 6

what is the difference between the asexual spores of basidio and ascomycetes and zygomycetes?

Answer 6

zygomycetes asexual spore is sporangiospore as opposed to conidium

Question 7

what is the structure of a basidiomycete?

Answer 7

basidiospores sit on top of the basidium, which is attached to the hypha

Question 8

what is the structure of an ascomycete?

Answer 8

ascospores contained within a sac (ascus)

Question 9

what is the structure of zygomycetes?

Answer 9

a rough walled zygote contains one or more zygospores

Question 10

what are yeasts?

Answer 10

fungi that favour a unicellular habit

Question 11

what diseases are caused by dermatophytes?

Answer 11

"ringworm" or TINEA:
capitis
facei
barbae
corporis
cruris
manum
pedis
unguium

Question 12

when would conidiophore be released?

Answer 12

when nutrients are low and the fungi needs to try and sporulate (spread)

Question 13

what are some causative agents of dermatophytosis (tinea)

Answer 13

epidermophyton microsporum and trichophyton spp

Question 14

what is a causative agent of pityriasis versicolor?

Answer 14

malassezia spp., which are yeasts that also form hyphae in infected skin

Question 15

when would a candida infection be fatal?

Answer 15

in immunocompromised patients where it can affect the deep organs.

Question 16

what host factors can increase pathogenicity of fungal infections?

Answer 16

favourable (warm, moist) micro environments
broad spectrum antibacterial agents can reduce competition for epithelial colonisation sites in the gut
any immunosuppression

Question 17

what different ways can a host become immunocompromised?

Answer 17

iatrogenic
disease processes
combinations of the above

Question 18

what are some examples of iatrogenic immunosuppression?

Answer 18

steroid
anti cancer chemo
solid organ transplantation

Question 19

what are some disease processes causing immunocompromisation?

Answer 19

AIDS
leukaemia
endocrinopathies

Question 20

what are risk factors for candidiasis?

Answer 20

age, antibiotic therapy, endocrine disorders, immune defects, immune suppression, surgery

Question 21

what is the most common type of candida species causing infection?

Answer 21

candida albicans

Question 22

are candida yeasts?

Answer 22

Yes

Question 23

can candida form hyphae?

Answer 23

Yes

Question 24

what would cause a chronic mucocutaneous infection?

Answer 24

genetic defects

and endocrine defects and immune defects

Question 25

what are the main causative species of aspergillosis?

Answer 25

aspergillus fumigatus

Question 26

what diseases can aspergillosis cause?

Answer 26

asthma aspergilloma asthma ith eosinophilia

Question 27

what type of fungus is apergillus?

Answer 27

mould

Question 28

how does aspergillosis infection occur?

Answer 28

inhalation of conidia

Question 29

what is a contributing factor to developing invasive pulmonary aspergillosis?

Answer 29

haematological malignancy

Question 30

what is the main causative species of cryptococcosis?

Answer 30

cryptococcus neoformans

Question 31

what diseases are caused by cryptococcus spp.

Answer 31

pulmonary cryptococcosis | meningitis (particularly in AIDS patients)

Question 32

what are some diagnostic methods of detecting fungal infections?

Answer 32

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

Question 33

how can dermatophytes be visualized?

Answer 33

directly in skin scales

Question 34

what are some different classes of antifungal drugs?

Answer 34

triazoles and allylamines echinocandins polyenes flucytosine

Question 35

what do triazoles and allylamines target?

Answer 35

sterols

Question 36

what do echinocandins target?

Answer 36

target cell wall

Question 37

what do polyenes target?

Answer 37

target the fungal cell membrane

Question 38

what does flucytosine target?

Answer 38

targets DNA synthesis

Question 39

what are some examples of polyenes?

Answer 39

amphotericin B | Nyastatin

Question 40

what are some examples of azoles?

Answer 40

clotrimazole fluconazole miconazole

Question 41

what are some examples of echinocandins?

Answer 41

anidulafungin caspofungin micafungin (IV)

Question 42

what are some problems with antigfungals?

Answer 42

``` spectrum of activity of the drug IV vs oral toxicity resistance cost static or cidal ```