Mycobacterium marinum

Background

• One of the non-tuberculous mycobacteria
• Environmental organism in fresh, brackish, or salt water
• Acquired through inoculation
• Rare cause of disease in humans
• Occupational risk of biologists, veterinarians, and fishermen

Clinical Manifestations

• Typically presents with nodular lymphangitis after exposure to fresh- or saltwater, including aquarium water ("fish tank granuloma")

Differential Diagnosis

• Other causes of nodular lymphangitis

Management

• For simple, localized lesion, can treat with monotherapy: clarithromycin, TMP-SMX, or doxycycline
• For other lesions, treat with combination clarithromycin and either ethambutol or rifampin
• Duration is for 1 to 2 months after resolution of lesions (typically 3 to 4 months total)