A Wood's lamp examination shows yellow-green fluorescence of scalp hairs in a child with tinea capitis. This fluorescence is produced by which dermatophyte group?
- A Trichophyton violaceum
- B Trichophyton tonsurans
- C Microsporum species (M. canis, M. audouinii) ✓
- D Epidermophyton floccosum
Correct answer: C. Microsporum species (M. canis, M. audouinii)
Explanation
Wood's lamp (filtered UV light at 365 nm) causes yellow-green fluorescence of scalp hairs in tinea capitis caused by Microsporum species (M. canis, M. audouinii, M. ferrugineum) due to production of pteridine metabolites. Trichophyton species (T. tonsurans, T. violaceum) do not fluoresce with Wood's lamp — yet T. tonsurans has largely replaced Microsporum in many parts of the world. Epidermophyton floccosum does not infect hair. This test is a useful rapid screening tool.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.