Mycetoma is most commonly caused by Streptomyces somaliensis.

• A. Streptomyces somaliensis
• B. Streptomyces griseus
• C. Streptomyces arenicola
• D. Streptomyces venezuelae

Answer: (A)

Mycetoma can be caused by either fungi (eumycetoma) or filamentous bacteria (actinomycetoma), and the actinomycetoma form is often linked to Streptomyces species. Among them, Streptomyces somaliensis is repeatedly reported as the most common cause of actinomycetoma, especially in endemic regions such as Africa and parts of Asia. Infection usually follows minor trauma that inoculates soil-dwelling bacteria into subcutaneous tissue, leading to a chronic lesion with draining sinuses and grain-like material. While other Streptomyces species can cause similar infections, Streptomyces somaliensis is the species most frequently associated with this condition, making it the best choice for “most commonly caused by.”