Paper II
2024 June (Supplementary) (2019 Scheme) · 100 marks · 180 min

Question

Laboratory diagnosis of mycetoma

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Answer

Laboratory diagnosis of mycetoma:

  • Direct examination of “grains” (discharged from sinus tracts) — crushed and examined microscopically; eumycetoma (true fungal) grains show broad, septate fungal hyphae, while actinomycetoma (bacterial/actinomycete) grains show fine, thin (<1 μm), branching filaments.
  • Gram stain and Modified Ziehl-Neelsen stain of crushed grains — distinguishes actinomycetoma (Gram-positive filaments, variably acid-fast for Nocardia) from eumycetoma (fungal hyphae, not acid-fast).
  • Culture — grains cultured on Sabouraud dextrose agar (for fungi, e.g., Madurella mycetomatis) and appropriate bacteriological media (for actinomycetes, e.g., Nocardia species), for definitive species identification — essential since treatment differs substantially between the two groups.
  • Histopathology — biopsy showing granulomatous inflammation with grains, using special stains (PAS/GMS for fungal elements) to characterize the causative organism.
  • Imaging (X-ray/MRI) — assesses extent of soft tissue and bone involvement.
  • Molecular methods (PCR) — increasingly used for species-level identification, particularly where culture is slow or unsuccessful.

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