WorksheetsMycology II
Total questions: 32
Worksheet time: 32mins
Yeast colonies are generally measured in:
mm
cm
nm
um
m
When we use the term glabrous to describe a fungal colony, which property of a colony Is it referring to?
surface pigmentation
topography
radius
reverse pigmentation
texture
How many classes of antifungal drugs are currently approved?
6
4
3
2
5
Which of the following is NOT an approved class of antifungal drug?
glycolipid inhibitors
triazoles
allylamines
echinocandins
none of the above
Which of the following classes of drugs targets the cell wall?
5'flycytosine
trizazoles
echinocandins
polyenes
allyamines
The antifungal drug nystatin binds to which component of the fungus?
ribosomal RNA machinery
chitin
mannoproteins
beta-glucans
ergosterol
Which of the following antifungal drugs should NOT be used as a monotherapy and why?
amphotericin B (AMB), as it requires IV administration
nystatin, as it is very poorly bioavailable
caspofungin, as resistance to it develops very quickly
fluconazole, as its a first-generation azole
5'flucytosine, as resistance to it develops very quickly
The ability of the yeast Cryptocococcus neoformans to grow in the presence of caspofungin is best described as:
intrinsic antifungal resistance
acquired antifungal resistance
long term antifungal resistance
transient antifungal resistance
antifungal resistance due to low bioavailability
A mechanism observed to underlie resistance in fungi to several classes of antifungal drug is:
inhibition of nucleic acid synthesis
modifications to efflux pumps
upregulation of cellular stress response
thickening of cell wall
none of the above
Mutations in the genes that underlie ergosterol biosynthesis in the fungal cell underlie resistance to which class of antifungal drugs?
polyenes
allylamines
echinocandins
flucytosine
none of the above
T or F. Fungal colonial morphology tells us whether the fungus is dimorphic
(a)
What needs to be described when looking at colonial morphology?
colony diameter
surface topography
surface texture
surface pigment
reverse pigment
What is an example of a dimorphic fungi?
Sporothirx spp.
Sporomyocin spp.
Spornate spp.
Sporotin spp.
T or F. Sporothrix schenckii lives in soil or plant matter & spores come into contact with skin through small cuts and scrapes. Also known as gardeners disease
(a)
T or F. The central feature of antifungal agents is the requirement for eukaryotic machinery to be differently blocked or destroyed in fungus BUT do limited or no damage to host cellular functions
(a)
What are the targets of an antifungal?
plasma membrane (azoles, polyenes and allylamines)
cell wall (echinocandins)
nucleic acid synthesis (flucytosine)
nucleus (ribocytine)
Select all that are correct about polyenes
bind to ergosterol to form a pore complex
disrupts plasma membrane leading to leakage of cytoplasmic contents
accumulation of ROS results in DNA, protein, mitochondrial and membrane damage
example drug is Amphotericin B
toxicity is not an issue (can bind to cholesterol and injure host cells)
Select all that are correct about azoles
inhibit ergosterol biosynthesis via cytochrome P450 enzyme 14-a demethylase
catalyses conversion of lanosterol to ergosterol
affects integrity of plasma membrane
uncommon class of antifungals
example drugs are imidazoles and triazoles
Select all that are correct about allylamines
inhibit early stages of ergosterol biosynthesis
targets the enzyme squalene epoxidase
inhibits integrity of plama membrane
highly effective against dermatophytes
example drugs are terbinafine and butenafine
Select all that are correct about echinocandins
target synthesis of B-1,3 glucans by blocking enzyme glucan synthase
causes decrease of glucose monomers linking B-1,3 and B-16 glucans
weakens cell wall and leads to fungal cell lysis
the first class of antifungals to be developed
example drugs are caspofungin, micafungin, anidulafungin
Select all that are correct about flucytosine
synthetic analogue of cytosine converted to 5-fluorouracil
5-fluorouracil encourages DNA and RNA synthesis
rapid development of resistance occurs during monotherapy
example drug is flucytosine
T or F. Superficial infections are caused by dermatophytes and yeasts
(a)
T or F. Invasive infections are a risk to healthy individuals
(a)
Fluconazole and nystatin can be used to treat superficial infections with yeasts like .....
Candida spp.
Aspergillus
Cryptococcus
E. coli
Terbinafine is successful in treating ....
dermatophytes
yeasts
arachnids
mosquito bites
Amphotericin B can be used to treat _______ but toxic to kidneys and requires IV
Aspergillus
Candida spp.
Cryptococcus
Streptococcus spp.
T or F. Antifungal tolerance is the ability to grow at drug concentrations above MICs that stop growth or kill most species
(a)
Select all that are correct
antifungal resistance can be classified as either intrinsic or acquired
intrinsic is not associated with drug exposure
acquired is associated with antifungal use
acquired isolates are not able to mutate
example of intrinsic is Cryptococcus neoformans
What is the correct sequence of mechanism for azoles
1. upregulation of stress response pathways
2. elevation of efflux pump activity that decreases drug concentrations in fungal cell
3. target site modification
2, 3, 1
1, 2, 3
3, 1, 2
2, 1, 3
What is the correct sequence of mechanism for echinocandins
1. point mutation in Fks1, Fks2, Fks3
2. genes encoding glucan synthase
3. upregulation of mechanisms protecting cell from stress
1, 2, 3
3, 2, 1
2, 3, 1
3, 1, 2
What is the correct sequence of mechanism for polyenes
1. thicker cell walls
2. upregulation of mechanisms protecting cells from stress
3. defects in ERG3 gene lead to accumulation of other sterols in fungal membrane
3, 1, 2
1, 2, 3
3, 2, 1
2, 3, 1
What is the correct sequence of mechanism for flucytosine
1. mutations in cytosine deaminase
2. mutations in USX1 gene in Cryptococcus spp.
3. mutations in uracil phosphoribosyl
3, 1, 2
2, 3, 1
1, 2, 3
3, 2, 1
