Question
Causative agents of mycetoma
Answer
Causative agents of mycetoma — distinguished into two categories, which is essential since treatment differs completely:
Eumycetoma (true fungal mycetoma): Madurella mycetomatis (the most common cause worldwide), Madurella grisea, Exophiala jeanselmei, Pseudallescheria boydii — grains typically black/dark-coloured, showing broad, septate fungal hyphae.
Actinomycetoma (bacterial mycetoma, caused by aerobic actinomycetes): Nocardia species (e.g., N. brasiliensis), Actinomadura species (A. madurae, A. pelletieri), Streptomyces somaliensis — grains typically white, yellow, or red, showing fine, thin, branching bacterial filaments.
Clinical distinguishing significance: eumycetoma requires antifungal therapy (itraconazole) often with surgical excision and generally has a poorer prognosis, while actinomycetoma typically responds well to prolonged combination antibacterial therapy (e.g., a sulfonamide-based regimen with an aminoglycoside).