L 66 Dermatophytoses and Subcutaneous Fungal Infections

Question 1

What are dermatophytes?

Answer 1

Fungi that invade keratin of skin, hair, nails

They have keratinase

Question 2

What are the 3 genera of dermatophytes?

Answer 2

Microsporum
-M canis
Trichophyton
-T rubrum
-T tonsurans
-T mentagrophytes
Epidermophyton
-E floccosum

Question 3

What is disease name for ringworm?

Answer 3

Tinea

Question 4

What are infective and diagnostic stages of ringworm?

Answer 4

Hyphae and arthroconidia

Question 5

How is ringworm spread?

Answer 5

Person to Person, direct contact
Nail salon
Head on chair

Question 6

Lab culture technique for onchomycosis/dermatophytes

Answer 6

Culture on Sabouraud agar or DTM=Dermatophyte Test Medium
DTM changes color to red in couple days, otherwise takes weeks to grow
10%KOH and cotton blue help to see arthroconidia

Question 7

What fluoresce under wood lamp?

Answer 7

Some Microsporum species

Remember that not all surface fungi will fluoresce

Question 8

What other fungal structures will be found in culture for identification?

Answer 8

Microconidium: small bud or ball coming off branch
Macroconidium: tennis racket looking thing

Question 9

What are arthroconidia?

Answer 9

This is the same structure that Cocci has. The hyphae essentially segment and break off like joints and form arthrospores that exist in the environment and infect

Question 10

What is trichophytin?

Answer 10

Crude antigen of dermatophytes

Question 11

What are some sources of dermatophytes to infect humans?

Answer 11

Zoophilic: animals
Anthrophophilic: human
Geophilic: soil

Question 12

How do the different dermatophytes present in the patient?

Answer 12

Clinical presentation of all the fungi in this group present similarly.
Tinea pedis may be caused by several fungi, but they will all present more or less the same and be treated the same

Question 13

Dermatophyte epidemiology

Answer 13

Like moist areas of body
more commonly tropical regions
Arthrospores are infective spores

Question 14

Characteristics of lesions

Answer 14

Inflamed at edges with central clearing
Hair loss with pruritis–can cause black spots from the broken hair
Scaling rash
Disseminated disease in HIV

Question 15

Dermatophyte risk factors

Answer 15

Hot tubs
Immunocompromised
Increased cortisol inhibits immune response
Athletics with body contact (wrestling)
Nail trauma, diabetes

Question 16

Most common dermatophyte in humans

Answer 16

T rubrum
T mentagrophytes (second)

Question 17

Dermatophytid reaction

Answer 17

Dermal reaction to fungal antigens, lesions devoid of organisms, hypersensitivity reaction, result of excessive treatment, most common in tinea pedis

Question 18

Dermatophyte treatment

Answer 18

Target ergosterol in cell membrane
Best treatment by taking drug internally (orally) and killing them from inside out, topical often won't work
Amphotericin B, Nystatin
Ketoconazole, Clotrimazole
Terconazole, Miconazole
Itraconazole, Tolnaftate
Griseofulvin, Lamisil (Terbinafine)
Remember that reinfection is likely! Throw away shoes etc.

Question 19

Treating with itraconazole

Answer 19

Treats onychomycosis

Pulse dosing prevents liver damage

Question 20

Dermatophyte control

Answer 20

Keep skin dry
Don’t share clothing or towels
Wear sandals
Don’t touch the lesions on others or on pets

Question 21

Most common agent causing tinea capitis

Answer 21

T tonsurans Endo/Ectothrix

Microsporum Ectothrix

Question 22

Treatment for tinea capitits

Answer 22

Griseofulvin DOC
itraconazole
terbinafine
fluconazole

Question 23

Agent for jock itch (tinea cruris)

Answer 23

Trichophyton rubrum

Question 24

Subcutaneous fungus attributes

Answer 24

Environmental in soil
TRAUMATIC INOCULATION
Chronic and subcutaneous
Chronic insidious

Question 25

Sporothrix schenckii characteristics

Answer 25

Thermally dimorphic (yeast and mold form)
Conidia – cluster resembles daisies
Chronic granulomas and necrosis
DOC: amphotericin B or itraconazole

Question 26

Sporothrix schenckii pathophysiology

Answer 26

Traumatic inoculation–often a gardener or someone spending lots of time with soil or decaying plant material
Develops abscesses, nodules, ulcers
Streaks up lymphatics
Usually self-limiting, except in immunocompromised

Question 27

Sporothrix schenckii diagnosis

Answer 27

Clusters of conidia on Sabouraud agar

Question 28

What is a mycetoma?

Answer 28

Tumor like infection of fungus

Question 29

Most common mycetoma in USA

Answer 29

Pseudallescheria boydii

Common foot disease?

Question 30

Fusarium causes of mycetomas

Answer 30

Tropical disease, foot, doesn’t respond well to treatment

Banana shaped macroconidia