L 66 Dermatophytoses and Subcutaneous Fungal Infections Flashcards Preview

Micro Exam 6 > L 66 Dermatophytoses and Subcutaneous Fungal Infections > Flashcards

Flashcards in L 66 Dermatophytoses and Subcutaneous Fungal Infections Deck (30):
1

What are dermatophytes?

Fungi that invade keratin of skin, hair, nails
They have keratinase

2

What are the 3 genera of dermatophytes?

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

3

What is disease name for ringworm?

Tinea

4

What are infective and diagnostic stages of ringworm?

Hyphae and arthroconidia

5

How is ringworm spread?

Person to Person, direct contact
Nail salon
Head on chair

6

Lab culture technique for onchomycosis/dermatophytes

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

7

What fluoresce under wood lamp?

Some Microsporum species
Remember that not all surface fungi will fluoresce

8

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

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

9

What are arthroconidia?

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

10

What is trichophytin?

Crude antigen of dermatophytes

11

What are some sources of dermatophytes to infect humans?

Zoophilic: animals
Anthrophophilic: human
Geophilic: soil

12

How do the different dermatophytes present in the patient?

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

13

Dermatophyte epidemiology

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

14

Characteristics of lesions

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

15

Dermatophyte risk factors

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

16

Most common dermatophyte in humans

T rubrum
T mentagrophytes (second)

17

Dermatophytid reaction

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

18

Dermatophyte treatment

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.

19

Treating with itraconazole

Treats onychomycosis
Pulse dosing prevents liver damage

20

Dermatophyte control

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

21

Most common agent causing tinea capitis

T tonsurans Endo/Ectothrix
Microsporum Ectothrix

22

Treatment for tinea capitits

Griseofulvin DOC
itraconazole
terbinafine
fluconazole

23

Agent for jock itch (tinea cruris)

Trichophyton rubrum

24

Subcutaneous fungus attributes

Environmental in soil
TRAUMATIC INOCULATION
Chronic and subcutaneous
Chronic insidious

25

Sporothrix schenckii characteristics

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

26

Sporothrix schenckii pathophysiology

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

27

Sporothrix schenckii diagnosis

Clusters of conidia on Sabouraud agar

28

What is a mycetoma?

Tumor like infection of fungus

29

Most common mycetoma in USA

Pseudallescheria boydii
Common foot disease?

30

Fusarium causes of mycetomas

Tropical disease, foot, doesn't respond well to treatment
Banana shaped macroconidia