Mycobacterium marinum lymphocutaneous infection

Area of Science:

• Microbiology
• Infectious Diseases
• Dermatology

Background:

• Mycobacterium marinum is a ubiquitous aquatic bacterium causing infections in fish and humans.
• Human infections typically manifest as cutaneous nodules but can involve deeper structures.
• Diagnosis of M. marinum infection is often delayed, posing a clinical challenge.

Observation:

• A 33-year-old man with no immunosuppression presented with sporotrichoid skin nodules on his hand and forearm.
• The patient's hobby involved maintaining a tropical fish aquarium.
• Skin biopsy showed a mycobacterial infection consistent with M. marinum, confirmed by molecular methods.

Findings:

• Histopathology and Ziehl-Neelsen staining revealed acid-fast bacilli in the skin biopsy.
• Molecular analysis confirmed Mycobacterium marinum as the causative agent.
• M. marinum was identified in the gut of a Poecilia reticulata (guppy) from the patient's aquarium.

Implications:

• This case highlights the transmission of Mycobacterium marinum from aquarium fish to humans.
• It underscores the importance of considering M. marinum in patients with relevant exposure history and sporotrichoid skin lesions.
• Successful treatment with a combination of clarithromycin, ethambutol, and rifampicin over 9 months demonstrates effective therapeutic options.