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
