7. Cutaneous and Subcutaneous Fungi

Question 1

Define “dermatophyte”

Answer 1

.

Question 2

define “tinea”

Answer 2

ringworm meaning lesion caused by fungal infection; lots of different terms (e.g. Tinea pedis = athlete’s foot); not species names, though! (thus not italicized)

Question 3

endothrix vs. ectothrix?

Answer 3

ectothrix is around hair vs. endothrix is fungal growth INSIDE the hair (GROSS)

Question 4

list the three genera of dermatophytic fungi and their shared characteristics

Answer 4

epidermophyton, microsporum, tricophyton

• mold form (filamentous) only (not dimorphic)
• produce both micro- and macro-conidia
• use keratin as nutrient (keratinase)
• do not invade living tissue
• rely on animal/human infection for species survival

Question 5

each pathogenic fungus is classified as ?

Answer 5

a mold (filamentous), a yeast or dimorphic

Question 6

Genera "Epidermophyton" (e.g. E. floccosum)
morphology?
source?
mode of spread?
role in causing outbreaks?

Answer 6

.

Question 7

Genera "Microsporum" (e.g. M. audouini)
morphology?
source?
mode of spread?
role in causing outbreaks?

Answer 7

.

Question 8

Genera "Tricophyton" e.g. (T. tonsurans)
morphology?
source?
mode of spread?
role in causing outbreaks?

Answer 8

.

Question 9

describe the dzs caused by fungal pathogens

Answer 9

.

Question 10

define the terms geophilic, zoophilic and anthrophilic and their utility in controlling outbreaks of superficial fungal disease.

Answer 10

zoophilic = fungal infection transmitted from animal to human
geophilic = soil to human
anthrophilic = human to human

The main utility of ID’ing the type of dermatophyte causing an outbreak of infections is that you can learn it is a zoophilic one and tx the animals.

Question 11

What is Tinea Versicolor?
Features?
What organism causes it?

Answer 11

• Superficial hyperpigmented, mycosis caused by member of the fungal biome.
• Dx w/ Wood’s lamp (black light) or with methylene blue on skin scales from infected area
• Malessezia sp. causes it

Question 12

What is Tinea Nigra?
Features?
What organism causes it?

Answer 12

• superficial

- common in tropical areas

Question 13

How are cutaneous mycoses dx’ed, tx’ed and prevented?

Answer 13

Dx: 1) stain using KOH and Calcofluor which binds chitin then direct microscopy, 2) culture in Saboraud’s agar (slow, weeks), 3) serology, 4) DNA probes
Tx: topical azoles or terbinafine; Rx = p.o. azoles, terbinafine, or griseofulvin; Ciclopirox solution for nails
Prevention: keep area dry and cool

Question 14

name and describe fungi that cause subcutaneous infections and describe the route of transmission

Answer 14

.

Question 15

how are subQ fungal infections dx’ed and tx’ed?

Answer 15

.

Question 16

..

Answer 16

..