A 35-year-old farmer in Maharashtra develops painless subcutaneous swelling on the foot with multiple sinuses discharging black granules. The most likely causative organism and its staining characteristics are:

• A Nocardia brasiliensis; white granules with acid-fast filaments
• B Actinomyces israelii; yellow sulfur granules
• C Sporothrix schenckii; cigar-shaped yeast on H&E stain
• D Madurella mycetomatis; black granules with melanin pigment on Fontana-Masson stain ✓

Explanation

Madurella mycetomatis is the most common cause of eumycetoma (fungal mycetoma) in India; it produces characteristic black granules composed of dark melanin-containing hyphae demonstrated by Fontana-Masson stain. Nocardia brasiliensis causes actinomycetoma (bacterial) with pale/white granules and partially acid-fast branching filaments. Actinomyces israelii causes cervicofacial actinomycosis with sulfur granules. Sporothrix causes lymphocutaneous sporotrichosis, not sinuses.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.