Medical microbiology – Buruli ulcer etiology: In clinical practice and public health examinations, which Mycobacterium species is recognized as the causative agent of Buruli ulcer (a necrotizing cutaneous infection producing undermined ulcers and mycolactone-mediated tissue destruction)?

Introduction / Context:
Buruli ulcer is a neglected tropical disease characterized by painless, undermined skin ulcers. Accurate identification of the etiological agent is vital for diagnosis, treatment selection, and epidemiological control. This question tests recognition of the specific Mycobacterium species responsible and distinguishes it from other non-tuberculous mycobacteria that cause cutaneous lesions.

Given Data / Assumptions:

• Disease: Buruli ulcer with necrotic skin lesions and extensive subcutaneous involvement.
• Pathogen candidates listed are non-tuberculous mycobacteria commonly implicated in skin/soft tissue infections.
• Answer must pinpoint the well-established causative agent.

Concept / Approach:
The hallmark of Buruli ulcer is the cytotoxic macrolide mycolactone, produced by Mycobacterium ulcerans. Mycolactone drives analgesia (painless lesions) and extensive tissue necrosis. Other species, such as Mycobacterium marinum, cause “fish tank granuloma,” typically presenting as nodular lymphangitis or papules following aquatic exposure, not the extensive undermined ulcers of Buruli disease. Rapid growers like Mycobacterium fortuitum and Mycobacterium chelonae can cause post-traumatic or post-procedural wound infections but are not the classical Buruli agents.

Step-by-Step Solution:
Identify the signature toxin (mycolactone) and link it to Mycobacterium ulcerans. Differentiate from M. marinum (aquarium granuloma) and rapid growers (M. fortuitum, M. chelonae) that have different clinical patterns. Select the species unequivocally associated with Buruli ulcer. Confirm therapeutic implications: combination antibiotics and surgical care are tailored to M. ulcerans.

Verification / Alternative check:
Epidemiological clustering in West Africa, Australia, and parts of Asia consistently isolates Mycobacterium ulcerans from lesions; molecular assays detect mycolactone polyketide synthase genes supporting causation.

Why Other Options Are Wrong:
Mycobacterium marinum causes aquatic-associated skin disease but not Buruli ulcer; Mycobacterium fortuitum and Mycobacterium chelonae are rapid growers tied to device or wound infections; Mycobacterium bovis primarily causes zoonotic tuberculosis and does not produce mycolactone.

Common Pitfalls:
Confusing any cutaneous NTM infection with Buruli ulcer; Buruli is specifically linked to M. ulcerans and its unique toxin.

Final Answer:
Mycobacterium ulcerans.