Flashcards in DL: Treatment of fungal skin disease Deck (11):
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
What advice would you give to an owner about M.canis infection?
- minimise contact
- wash hands and arms thoroughly
- inform of human CS and go to doctor
- bedding hygiene
- vacuum and disinfection (dilute bleach works wells)
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)
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)
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
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.
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.
What is the mode of action of imidazoles?
Alter cell membrane permeability (by blocking the synthesis of ergosterol the primary cell sterol of fungi).
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.
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.