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Liz's Mycology Course > Dermatophytes > Flashcards

Dermatophytes Flashcards

1
Q

Fungus that infects the skin, hair, or nails (due to presence of keratin) in humans or animals

A

Dermatophyte

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2
Q

Dermatophytosis of the head

A

Tinea capitus

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3
Q

Dermatophytosis of the body

A

Tinea corporis

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4
Q

Dermatophytosis of beards

A

Tinea barbae

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5
Q

Dermatophytosis of the groin (aka “jock itch”)

A

Tinea cruris

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6
Q

Dermatophytosis of the feet (athlete’s foot)

A

Tinea pedis

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7
Q

Dermatophytosis of the nail

A

Tinea unguium

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8
Q

Nail infection caused by non-dermatophytes

A

Onchomycosis

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9
Q

Dermatophytosis

A

Aka ringworm

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10
Q

Why do dermatophytes generally only infect hair, skin, and nails?

A

They use keratin as their nitrogen source (invasion of the deeper tissues is very rare)

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11
Q

List the various ways to detect dermatophyte infections

A
  • Direct physical examination (Wood’s lamp - UV)
  • Lab examination of specimen (skin scraping, hair, toenail, etc.)
  • Cultures
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12
Q

What are some lab examination methods?

A
  • KOH
  • Calcufluor white (fungi fluoresce)
  • Ectothrix vs. endothrix invasion (in vivo)
  • Hair perfusion test (in vitro)
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13
Q

Describe the culture method used for dermatophytes

A
  • Primary isolation medium + cyclohexamide to kill skin contaminants (Mycosel or mycobiotic agar)
  • Incubate 2-4 weeks (recommended 30 days)
  • Most have fluffy white growth
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14
Q

Trichophyton rubrum

- Colony formation

A
  • White and fluffy or granular
  • Reverse is cherry red (>3 weeks)
    VERY DISTINCT!!!!!
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15
Q

Trichophyton rubrum

- Microscopic formation

A
  • Tiny teardrop microcondria (“birds on a wire”)
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16
Q

Trichophyton mentagrophytes

- Colony formation (2 types)

A
  • Downy → specimen from feet

- Granular → infections spread form animals

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17
Q

Trichophyton mentagrophytes

- Microscopic formation

A
  • Spiral hyphae
  • Tear-shaped microconidia often in grape-like clusters
  • Macroconidia are cigar-shaped
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18
Q

What two microscopic forms do you need to see in order to identify Trichophyton mentagrophytes?

A
  • Macroconidia and spiral hyphae OR

- Macroconidia and tear-shaped microconidia in grape-like clusters

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19
Q

Trichophyton tonsurans

- Colony formation

A
  • Buff/brown (may be rust colored on reverse), wrinkled, or cratered
  • Grows poorly on most media → enhanced by thiamin (T4 agar vs. T1 agar)
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20
Q

Trichophyton tonsurans

- Microscopic formation

A

Elongated balloons OR stretched teardrops

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21
Q

Trichophyton verrucosum

- Colony formation

A

Enhanced growth @ 37°C

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22
Q

Trichophyton verrucosum

- Microscopic formation

A
  • “Antler” hyphae

- Chlamydoconidia “armadillo/rat tails”

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23
Q

Trichophyton schoenleinii

- Colony formation

A

Gray and white

24
Q

Trichophyton schoenleinii

- Microscopic formation

A
  • “Club/antler-shaped” hyphae and “favic chandeliers”

- CONIDIA ARE RARE!

25
Q

Epidermophyton floccosum

- Colony formation

A

Tan to yellowish to khaki

26
Q

Epidermophyton floccosum

- Microscopic formation

A

Macroconidia are smooth, thin-walled, club-shaped (“beavers tail”), 2-4 cells
- NO MICROCONIDIA!

27
Q

Microsporum canis

- Colony formation

A
  • Fluffy or granular

- Reverse is bright yellow (w/ continued growth)

28
Q

Microsporum canis

- Microscopic formation

A
  • Macroconidia have thick, rough walls consisting of 3-15 cells and having a curved tip
29
Q

Microsporum gypseum

- Colony formation

A
  • Powdery, buff/cinnamon colored

- Reverse is yellow/orange/brown

30
Q

Microsporum gypseum

- Microscopic formation

A

Macroconidia are ellipsoidal w/ rounded blunt ends, thin cell wall, 2-7 cells

31
Q

Microsporum audouini

- Colony formation

A

Cottony white, slow growing

32
Q

Microsporum audouini

- Microscopic formation

A

Terminal chlamydoconidia and comblike (pectinate) hyphae

33
Q

How do you differentiate T. rubrum from T. mentagrophytes using the hair perforation testing?

A
  • T. rubrum → hair perforation NEGATIVE

- T. mentagrophytes → hair perforation POSITIVE

34
Q

Microsporum genus

- Amt of macroconidia vs. microconidia

A

Many macroconidia/few microconidia

35
Q

Trichophyton genus

- Amt of macroconidia vs. microconidia

A

Few macroconidia/many microconidia

36
Q

Epidermophyton genus

- Amt of macroconidia vs. microconidia

A

ONLY macroconidia

37
Q

Which dermatophyte is the #1 cause of dermatophyte infections?

A

Trichophyton tonsurans

38
Q

Which dermatophyte is the #2 of dermatophyte infections?

A

Trichophyton rubrum

39
Q

Most common cause of favus (tinea capitus)

A

Trichophyton schoenleinii

40
Q

Most common cause of “tinea gladatorium”

A

Trichophyton tonsurans

41
Q

Most common cause of cattle farmer dermatophyte infections

A

Trichophyton verrucosum

42
Q

Most common cause of dog/cat dermatophyte infections

A

Microsporum canis

43
Q

Most common cause of tinea versicolor

A

Malassezia furfur

44
Q

Most common soil fungus

A

Microsporum gypseum

45
Q

Which dermatophyte does NOT fluoresce w/ a Wood’s lamp?

A

Trichophyton species

46
Q

What is the most likely infective area for Trichophyton species?

A

Hair, skin, nails

47
Q

What is the most likely infective area for Epidermophyton species?

A

Skin and nails

48
Q

What is the most likely infective area for Microsporum species?

A

Skin and hair

49
Q

Which dermatophyte is urease NEGATIVE?

A

Trichophyton rubrum

50
Q

Which dermatophyte is urease POSITIVE?

A

Trichophyton mentagrophytes

51
Q

Which dermatophyte fluoresces yellow-green w/ a Wood lamp?

A

Microsporum canis

52
Q

Which dermatophyte causes an endothrix infection in the hair?

A

Trichophyton tonsurans

53
Q

Which dermatophyte causes an ectothrix infection in the hair?

A

Microsporum canis

54
Q

This infection is living (usually forming a spore sheath) on the surface of hair, as well as growing w/in the hair shaft

A

Ectothrix

55
Q

This infection is growing w/in the hair shaft w/o a conspicuous external sheath of spores

A

Endothrix

- Hair breaks at scalp (“Black Dot”)

56
Q

Which dermatophytosis is another cause of “black dot”?

A

Tinea capitus

Liz's Mycology Course (8 decks)

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