Paper I — 2022 July (Supplementary) (2019 Scheme) — Q11
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Paper I
2022 July (Supplementary) (2019 Scheme) · 100 marks · 180 min
Question
Lab diagnosis of Ring worm infection
Q114 marksShort Answers
Answer
Laboratory diagnosis of ringworm (dermatophyte) infection:
Wood’s lamp examination — some Microsporum species show characteristic green fluorescence of infected hair under UV light (most Trichophyton species do not fluoresce); useful for tinea capitis screening.
Direct KOH microscopy — of skin scrapings, hair, or nail clippings, demonstrating septate, branching hyphae; the standard rapid first-line test.
Culture — on Sabouraud dextrose agar (with cycloheximide to inhibit contaminating environmental fungi); colony morphology, pigmentation, and microscopic conidial morphology (macroconidia/microconidia shape) allow species identification.
Slide culture technique — for undisturbed examination of fruiting structures/conidial arrangement when precise species identification is needed.
Specimen collection: scraping from the active, advancing edge of a skin lesion (highest fungal load); hair pluck (not cut hair) for tinea capitis; nail clippings/subungual debris for onychomycosis.
