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Flashcards in DL: Treatment of fungal skin disease Deck (11):
1

What steps would you take to show that lesions are due to dermatophytosis? 4

- Wood's Lamp Exam
- Microscopy (skin scrapes and hair plucks to look for hyphae and arthroconidia)
- Fungal culture (Sabaroud's material preferable to Dermatophyte growth medium)
- Skin biopsies

2

What advice would you give to an owner about M.canis infection?

- zoonotic
- minimise contact
- wash hands and arms thoroughly
- inform of human CS and go to doctor
- bedding hygiene
- vacuum and disinfection (dilute bleach works wells)

3

What the the possible treatments for M.canis

- TOPICAL - shampoo, targets stratum corneum but not hair invasion
- SYSTEMIC - itraconazole, needed to clear infection (along with cell mediated immunity as topical therapy isn't sufficient)

4

Give a treatment protocol for a cat with M.canis

- ITRACONAZOLE (systemic) - 3 cycles of therapy, one week on one week off (as cumulatese in stratum corneum and keratinised tissue so administration every week isn't necessary_
- MICONAZOLE AND CHLORHEXIDINE shampoo (topical, 2% each)
- clip hair around lesion, across whole body if widespread
- (Griseofulvin no longer available)

5

Why are antifungals generally less effective and more toxic than antibacterials?

Fungi like mammals are eukaryotes (unlike bacteria) therefore more similar to human/host cells than bacteria so host cells may well be targeted with the therapy as well as the fungus itself

6

How do polyenes such as amphotericin B and nystatin work?

bind to sterols and form hydrophobic channels. Binds to ergosterol (fungi) and cholesterol (mammal) and therefore causes adverse effects to the fungi and the host.

7

Are imidazole and triazole antifungals more or less useful that polyenes and 5-fluorocytosine?

Imidazole and triazole because they have a wider spectrum of activity, there is no prevalent resistance against them, they have fewer side effects. Also polyenes are poorly absorbed from the GIT.

8

What is the mode of action of imidazoles?

Alter cell membrane permeability (by blocking the synthesis of ergosterol the primary cell sterol of fungi).

9

How does f-fluorocytosine work?

incorporated into fungal DNA after conversion from 5-FU. Human/pet not affected by this but the problem with its use relates to fungal resistance to it.

10

Outline a treatment protocol for Malassezia dermatitis

- 2% miconazole/ 2% chlorhexidine (every 3 days for 3 weeks until controlled). Good evidence when given twice weekly.
- systemic - possible but more expensive, ketoconazole or itraconazole. Only fair EBVM for these though.

11

What is an appropriate treatment for Histoplasma infection (a dimorphic yeast) in a dog with signs of wasting and lung infection.

Systemic antifungal (itraconazole) with amphotericin B if there is systemic spread.

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