A farmer from Tamil Nadu presents with a painless swelling on the foot with multiple discharging sinuses containing black granules. He reports working barefoot for years. The granules are crushed and show branched septate hyphae. What is the MOST likely causal organism of this mycetoma?
- A Nocardia brasiliensis — black grains indicate actinomycetoma
- B Madurella mycetomatis — black grains indicate true fungal (eumycetoma) infection ✓
- C Sporothrix schenckii — black grains on microscopy are diagnostic
- D Aspergillus fumigatus — invasive aspergillosis of soft tissue
Correct answer: B. Madurella mycetomatis — black grains indicate true fungal (eumycetoma) infection
Explanation
Mycetoma (Madura foot) is characterised by a triad of tumefaction, draining sinuses and grains. Black/dark grains + septate hyphae = eumycetoma (fungal mycetoma) caused most commonly by Madurella mycetomatis. White/yellow grains that on crush show filamentous bacterial (1 µm wide) chains = actinomycetoma (Actinomadura madurae, Nocardia brasiliensis). Sporothrix schenckii causes sporotrichosis (dimorphic, lymphocutaneous nodules) — not mycetoma. Black grain eumycetoma is treated with surgical debridement plus prolonged itraconazole/voriconazole.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.