Dermatophytes: Difference between revisions
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= Species and Classification = |
== Species and Classification == |
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* Three common genii: |
* Three common genii: |
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* Three categories: anthropophilic, zoophilic, and geophilic |
* Three categories: anthropophilic, zoophilic, and geophilic |
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= Presentation = |
== Presentation == |
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* Clinical presentation is usually ringworm |
* Clinical presentation is usually ringworm |
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** Tinea unguun: nails |
** Tinea unguun: nails |
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= Diagnosis = |
== Diagnosis == |
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== Specimen collection == |
=== Specimen collection === |
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* Hair: need the root, with sterile forceps |
* Hair: need the root, with sterile forceps |
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* Nails: alcohol gauze to clean, then scrape subungual debris |
* Nails: alcohol gauze to clean, then scrape subungual debris |
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== Laboratory Testing == |
=== Laboratory Testing === |
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* Direct microscopy: KOH (potassium hydroxide) calcofluor of skin scraping, under UV light |
* Direct microscopy: KOH (potassium hydroxide) calcofluor of skin scraping, under UV light |
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** Incubate for 2-3 weeks at 30ºC |
** Incubate for 2-3 weeks at 30ºC |
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== Indentification == |
=== Indentification === |
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* Chemical properties |
* Chemical properties |
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Revision as of 19:31, 15 August 2019
Species and Classification
- Three common genii:
- Epidermophyton
- Microsporum
- Trichophyton
- Three categories: anthropophilic, zoophilic, and geophilic
Presentation
- Clinical presentation is usually ringworm
- Most active form in the periphery of the ring
- Can invade immunocompromised patients, e.g. Majocchi's granuloma and kerion
- Named by anatomic location
- Tinea capitis: head
- Tinea corporis: body
- Tinea cruris: groin
- Tinea unguun: nails
Diagnosis
Specimen collection
- Hair: need the root, with sterile forceps
- Skin: disinfect with alcohol or sterile water, then scrape the border with a blunt scalpel
- Nails: alcohol gauze to clean, then scrape subungual debris
Laboratory Testing
- Direct microscopy: KOH (potassium hydroxide) calcofluor of skin scraping, under UV light
- Culture with Littman agar w streptomycin, Sabouraud agar with chloram+gent, Sabouraud agar with CG+cyclohexamide
- Incubate for 2-3 weeks at 30ºC
Indentification
- Chemical properties
- Growth at 37ºC
- Urease production/urea hydrolysis
- BCP-MSG reaction (important)
- Hair perforation test
- Vitamin requirements with trichophyton agars T1 to T7
- Growth on polished rice grain
- Colony features
- Speed of growth
- Colour on surface
- Texture
- Colour on reverse
- Microscopic features
- Macroconidia, microconidia, septae
