Dermatophytes

Question 1

fungi that infect superficial areas of body, such as hair, skin and nails

Answer 1

dermatophyte

Question 2

Infection of keratinized tissue

Answer 2

dermatophytosis

Question 3

Infections of the head

Answer 3

tinea capitis

Question 4

infections of the body

Answer 4

tinea corporis

Question 5

infections of the beard

Answer 5

tinea barbae

Question 6

infections of the groin (jock itch)

Answer 6

tinea cruris

Question 7

infections of the foot (athlete’s foot)

Answer 7

tinea pedis

Question 8

infections of the nail

Answer 8

tinea unguium

Question 9

nail infection by non-dermatophytes

Answer 9

onchomycosis

Question 10

Dermatophyte infections are commonly referred to as “tinea” or “_______”

Answer 10

ringworm

Question 11

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

Answer 11

They use keratin as nitrogen source

Question 12

What is the most common of human fungal infections

Answer 12

dermatophyte

Question 13

What are the three ways to identify a dermatophyte infection?

Answer 13

• Direct physical examination
• Lab examination of specimen (skin scraping, hair, toenail)
• Culture

Question 14

What are 4 Direct Physical Exams

Answer 14

1. Wood’s lamp (UV)
2. Potassium hydroxide (KOH)
3. Calcoflour white - fungi fluoresce
4. Exam of hair for ectothrix or endothrix invasion

Question 15

In Wood’s Lamp Exam:

• Microsporum in hair fluoresces ________
• Skin with tine versicolor fluoresces ________
• Trichophyton fluoresces _________

Answer 15

• yellow-green
• yellow
• does NOT fluoresce

Question 16

Culture:

- what medium and what does it do?

Answer 16

Primary isolation medium + cyclohexamide to kill skin contaminants (CSAB) (Mycosel or Mycobiotic Agar)

Question 17

Culture:

- incubation time?

Answer 17

2-4 weeks (recommended 30 days)

Question 18

Most identifications are by ______ ______

Answer 18

microscopic morphology (microconidia/macroconidia)

Question 19

Trichophyton infects what?

Answer 19

hair, skin, and nail (especially feet and nails)

Question 20

Trichophyton:

- Microconidia vs Macroconidia

Answer 20

Microconidia: important for identification
Macroconidia: rarely helpful

Question 21

Trichophyton:

• other tests available?
• does it fluoresce with Wood’s lamp?

Answer 21

• Biochemical tests available

- does NOT fluoresce

Question 22

Second most common cause of dermatophytosis

Answer 22

Trichophyton rubrum

Question 23

Trichophyton rubrum:

- Reverse

Answer 23

most are cherry red (>3 weeks)

Question 24

Trichophyton rubrum:

- What do they look like?

Answer 24

tiny teardrop microconidia; “birds on a wire”

Question 25

Trichophyton rubrum | - Urease reaction

Answer 25

negative

Question 26

Trichophyton rubrum | - Hair perforation reaction

Answer 26

Negative

Question 27

Trichophyton mentagrophytes: | - 2 types of colonies

Answer 27

- downy: from feet | - granular: infection spread from animals

Question 28

Trichophyton mentagrophytes: | - reverse

Answer 28

May be red/brown (medium dependent)

Question 29

Trichophyton mentagrophytes: | - microscopic mold appearance

Answer 29

- hyphae may be spiral shaped - tear-shaped microconidia often in grape like clusters - macroconidia cigar shaped

Question 30

Trichophyton mentagrophytes: | - urease reaction

Answer 30

Positive

Question 31

Trichophyton mentagrophytes: | - hair perforation test reaction

Answer 31

Positive

Question 32

#1 cause of tinea capitis in US (especially children) and wrestlers, hence "tinea gladiotorium)

Answer 32

Trichophyton tonsurans

Question 33

Trichophyton tonsurans: | - Colonies

Answer 33

Buff/brown (May be rust colored on reverse), wrinkled or cratered

Question 34

Trichophyton tonsurans: | - Microconidia appearance

Answer 34

Elongated balloons or stretched teardrops

Question 35

Trichophyton tonsurans: | - grows poorly on most media, growth enhanced by __________

Answer 35

Thiamin (T4 agar vs T1 agar)

Question 36

Trichophyton tonsurans: | - any hair infection?

Answer 36

Endothrix infection (fungus inside hair shaft), hair brakes at scalp ( "Black dot")

Question 37

Trichophyton verrucosum: | - causes tinea ______

Answer 37

Capitus (another cause of "black dot")

Question 38

Trichophyton verrucosum: | - what type of people are at risk

Answer 38

Cattle/dairy workers

Question 39

Trichophyton verrucosum: | - lesions often misdiagnosed as what type of infection

Answer 39

Staph infection

Question 40

Trichophyton verrucosum: | - microscopic appearance

Answer 40

"antler hyphae" and chlamdoconidia "armadillo/rat tails"

Question 41

Trichophyton verrucosum: | - Will it grow at 37°C

Answer 41

- growth is enhanced at 37°C

Question 42

Trichophyton schoenleinii: | - what infection does it cause

Answer 42

- causes favus (tinea capitus) - scarring and permanent hair loss (yellow, thickened, cup shaped crusts)

Question 43

Trichophyton schoenleinii: | - colony appearance

Answer 43

Gray and waxy

Question 44

Trichophyton schoenleinii: | - microscopic appearance

Answer 44

- conidia are rare, club/antler shaped hyphae and "favic chandeliers" - branching hyphae seen within hairs (tunnels)

Question 45

Trichophyton schoenleinii: | - common in what countries

Answer 45

Appalachia and Scandinavian countries