ID

Mycobacterium marinum

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Mycobacterium marinum

Pathophysiology
Causes Nodular Lymphangitis

Mycobacterium marinum most common etiology
Other atypical Mycobacteria can also cause

Exposure risks
Fresh and Saltwater Exposure

Fish Handlers
Tropical aquarium keepers (fish tanks)
Swimming in ocean water, lakes, and pools

Signs

Primary lesion after 2-8 week incubation
1. Papular lesion develops at inoculation site
Secondary lesions
1. Erythematous Papules, Nodules develop up lymph chain
2. Lesions ulcerate or form abscess
Systemic symptoms are rare
1. Fever
2. Regional adenopathy

Differential Diagnosis

See Nodular Lymphangitis

Labs

Microscopic examination
1. Organisms rarely seen
Culture of biopsied tissue
1. Requires special incubation Temperatures
Purified Protein Derivative (PPD)
1. Usually >10 mm in active Mycobacterium marinum cases

Management

Apply warm compresses for 40 to 60 minutes per day
Antibiotics for 2-3 months after symptom resolution
1. Combination Protocol 1
  1. Clarithromycin 30 mg/kg/day and
  2. One of the following
    1. Rifampin 10-15 mg/kg/day or
    2. Ethambutol 25 mg/kg/day
2. Combination Protocol 2
  1. Rifampin 15 mg/kg/day and
  2. Ethambutol 25 mg/kg/day
3. Alternative Antibiotic option (based on sensitivity)
  1. Minocycline 100 mg PO bid

References