Flashcards in Dermatophytes & Malassezia Deck (32)
Describe the colony characteristics of M. canis
white top surface
flat w/ depressed center
Describe the macroconidia of M. canis
> 6 cells
thick cell walls
Describe the colony characteristics of M. gypseum
cinnamon brown top
Describe the macroconidia of M. gypseum
Describe the colony characteristics of T. mentagrophytes
Describe the microcondia of T. mentagrophytes
Describe the colony characteristics of M. nanum
white to buff top
Describe the macroconidia of M. nanum
Describe the colony characteristics of T. rubrum
white top surface
Describe the macroconidia and microconidia of T. rubrum
macro: pencil-cigar shaped
micro: club-shaped to pyriform along hyphae
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
What is the color change seen in DTM w/ fungal growth?
Yellow--> red due to alkaline metabolites produced by dermatophytes
What metabolite is responsible for fluorescence of M. canis under Wood's lamp exam?
pteridine (Clinical consensus guidelines of dermatophytosis)
What do you add to a horse DTM culture sample to grow T. equinum?
Vitamin B--> requires niacin for growth
What do you add to a horse DTM culture sample to grow T. verrucosum?
Vitamin B--> requires thiamine for growth
What is the wavelength of light involved in Wood's lam examination?
253.7 nm (SAD)
360 nm (Clinical consensus guidelines of dermatophytosis)
What are the ideal conditions for DTM culture?
30 degrees C and 30% humidity
How often do you check DTM culture plates?
daily for growth AND color change up to 14 days
What is a derm duet plate?
one side Sabouraud dextrose agar...may be easier to grow macroconidia
other side DTM
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
Which species of dermatophyte can cause reverse zoonosis?
What is the causative agent of athlete's foot in people?
Name 3 treatment strategies for dermatophytosis in catteries or multi-cat households?
1. Total depopulation
2. Treat all animals
3. Treat kittens only
How long can M. canis spores remain viable in the environment?
Name the components of the fungal cell wall.
2. Beta 1-3 glucans
What is the IHC gene for dermatophytes?
chitin synthase 1
Which species of Malassezia is non-lipid dependent?
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
Which metabolite is responsible for the pigment change associated w/ Tinea versicolor?
azelaic acid metabolite--> inhibits tyrosinase--> hypopigmentation