Flashcards in Dermatophytes & Malassezia Deck (32)
Loading flashcards...
1
Describe the colony characteristics of M. canis
white top surface
yellow/orange undersurface
flat w/ depressed center
cotton/wooly consistency
2
Describe the macroconidia of M. canis
terminal knob
> 6 cells
thick cell walls
outer spines
3
Describe the colony characteristics of M. gypseum
cinnamon brown top
tan undersurface
flat
powdery consistency
4
Describe the macroconidia of M. gypseum
<6 cells
thin walls
5
Describe the colony characteristics of T. mentagrophytes
white-cream top
tan undersurface
6
Describe the microcondia of T. mentagrophytes
spiral hyphae
7
Describe the colony characteristics of M. nanum
white to buff top
red-brown undersurface
downy-powdery consistency
8
Describe the macroconidia of M. nanum
1-3 cells
pear-egg shape
numerous
9
Describe the colony characteristics of T. rubrum
white top surface
red-brown under
downy
10
Describe the macroconidia and microconidia of T. rubrum
macro: pencil-cigar shaped
micro: club-shaped to pyriform along hyphae
11
Name the components of the DTM
1. Sabouraud's dextrose agar
2. cycloheximide: anti-fungal
3. gentamicin: antibiotic
4. chlortetracycline: antibiotic
5. Phenol red: color change
12
What is the color change seen in DTM w/ fungal growth?
Yellow--> red due to alkaline metabolites produced by dermatophytes
13
What metabolite is responsible for fluorescence of M. canis under Wood's lamp exam?
tryptophan (SAD?)
pteridine (Clinical consensus guidelines of dermatophytosis)
14
What do you add to a horse DTM culture sample to grow T. equinum?
Vitamin B--> requires niacin for growth
15
What do you add to a horse DTM culture sample to grow T. verrucosum?
Vitamin B--> requires thiamine for growth
16
What is the wavelength of light involved in Wood's lam examination?
253.7 nm (SAD)
360 nm (Clinical consensus guidelines of dermatophytosis)
17
What are the ideal conditions for DTM culture?
30 degrees C and 30% humidity
18
How often do you check DTM culture plates?
daily for growth AND color change up to 14 days
19
What is a derm duet plate?
one side Sabouraud dextrose agar...may be easier to grow macroconidia
other side DTM
20
Why is KOH more commonly used on human samples to evaluate for dermatophytosis than animal samples?
Human infections are more endothrix...need to remove keratin first w/ KOH
animal infections more ectothrix infection...spores on the outside of the hair shaft
21
Which species of dermatophyte can cause reverse zoonosis?
Trichophyton rubrum
22
What is the causative agent of athlete's foot in people?
Trichophyton rubrum
23
Name 3 treatment strategies for dermatophytosis in catteries or multi-cat households?
1. Total depopulation
2. Treat all animals
3. Treat kittens only
24
How long can M. canis spores remain viable in the environment?
18-24 months
25
Name the components of the fungal cell wall.
1. Mannoproteins
2. Beta 1-3 glucans
3. chitin
4. ergosterol
26
What is the IHC gene for dermatophytes?
chitin synthase 1
27
Which species of Malassezia is non-lipid dependent?
M. pachydermatis
28
Which species of Malassezia are lipid dependent?
1. M. furfur
2. M. globosa
3. M. obtuse
4. M. restricta
5. M. slooffiae
6. M. sympodialis
29
Which metabolite is responsible for the pigment change associated w/ Tinea versicolor?
azelaic acid metabolite--> inhibits tyrosinase--> hypopigmentation
30
