Mycobacterium marinum

1. Pathophysiology: Causes Nodular Lymphangitis
   1. Mycobacterium marinum most common etiology
   2. Other atypical Mycobacteria can also cause
2. Exposure risks: Fresh and Saltwater Exposure
   1. Fish Handlers
   2. Tropical aquarium keepers (fish tanks)
   3. Swimming in ocean water, lakes, and pools
3. Signs
   1. Primary lesion after 2-8 week incubation
      1. Papular lesion develops at inoculation site
   2. Secondary lesions
      1. Erythematous Papules, Nodules develop up lymph chain
      2. Lesions ulcerate or form abscess
   3. Systemic symptoms are rare
      1. Fever
      2. Regional adenopathy
4. Differential Diagnosis
   1. See Nodular Lymphangitis
5. Labs
   1. Microscopic examination
      1. Organisms rarely seen
   2. Culture of biopsied tissue
      1. Requires special incubation Temperatures
   3. Purified Protein Derivative (PPD)
      1. Usually >10 mm in active Mycobacterium marinum cases
6. Management
   1. Apply warm compresses for 40 to 60 minutes per day
   2. 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
7. References
   1. Edelstein (1994) Arch Intern Med 154:1359-64 [PubMed]
   2. Lewis (2003) Clin Infect Dis 37:390-7 [PubMed]
   3. Tobin (2001) Am Fam Physician 63:326-32 [PubMed]