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Flashcards in Dermatophytes & Malassezia Deck (32)
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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

How does Malassezia adhere to the skin surface?

trypsin-sensitive protein adhesion