Dermatophytes: Difference between revisions
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== Species and Classification == |
== Species and Classification == |
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* Three common genii: ''Epidermophyton'', ''Microsporum'', and ''Trichophyton'' |
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* Three common genii: |
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** Epidermophyton |
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** Microsporum |
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** Trichophyton |
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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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** Can invade immunocompromised patients, e.g. Majocchi's granuloma and kerion |
** Can invade immunocompromised patients, e.g. Majocchi's granuloma and kerion |
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* Named by anatomic location |
* Named by anatomic location |
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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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* Skin: disinfect with alcohol or sterile water, then scrape the border with a blunt scalpel |
* Skin: disinfect with alcohol or sterile water, then scrape the border with a blunt scalpel |
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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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* Culture with Littman agar w streptomycin, Sabouraud agar with chloram+gent, Sabouraud agar with CG+cyclohexamide |
* Culture with Littman agar w streptomycin, Sabouraud agar with chloram+gent, Sabouraud agar with CG+cyclohexamide |
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=== Indentification === |
=== Indentification === |
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* Chemical properties |
* Chemical properties |
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** Growth at 37ºC |
** Growth at 37ºC |
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Revision as of 01:32, 31 January 2020
Species and Classification
- Three common genii: Epidermophyton, Microsporum, and Trichophyton
- Three categories: anthropophilic, zoophilic, and geophilic
Presentation
- Clinical presentation is usually as ringworm
- Most active form is 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
