Mycobacterium marinum


  • Atypical Mycobacterium species found in fresh or salt water (cold or warm)
  • Bacteria that causes "fish tank Granuloma"
  • Can infect both immunocompetent and immunocompromised hosts
  • M. marinum is generally not found in chlorinated swimming pools[1]

Risk Factors

  • Aquarium workers and enthusiasts
  • Swimming
  • Handling of contaminated water

Clinical Features

Fish tank granuloma. [2]
Fish tank granuloma spreading via lymphatic channels.
  • Solitary to multiple superficial red nodules or plaques in exposed areas
    • Lesions on the hands and fingers if works with aquariums, or the knees and elbows in swimmers
  • Ascending lymphangitis that resembles sporotrichosis

Differential Diagnosis

Skin and Soft Tissue Infection



  • Clinical diagnosis in ED
  • Can be aided by histopathology
  • If there is an affected joint it is important to evaluate for a septic arthritis
  • If there are draining wounds consider imaging and evaluate for osteomyelitis


  1. Long-term antibiotic therapy (2-18 weeks)
  2. Warm compresses (bacterium is heat-sensitive)


  • Unless the patient has evidence of sepsis, severe pain, or has other severe complicating medical problems, outpatient treatment is acceptable.

Clinical Course

  • M marinum infection may result in non-healing ulcers or a septic arthritis.
  • Aggressive or long standing . marinum infection may cause severe osteomyelitis requiring surgical debreedment

See Also

External Links


  1. Slany M et al. Mycobacterium marinum infections in humans and tracing of its possible environmental sources. Can J Microbiol. 2012. 58(1): 39-44
  2. Ryan, J and Bryant G. "Fish tank granuloma - a frequently misdiagnosed infection of the upper limb." J Accid Emerg Med. 1997 Nov; 14(6): 398–400.
  3. Petrini, B; "Mycobacterium Marinum: ubiquitous Agent of Waterborne Granulomatous Skin Infections." European Journal of Clinical Microbiology and Infectious Diseases. October 2006, Volume 25, Issue 10, pp 609-613
  4. Rallis, E; Koumantaki-Mathioudaki, E; "Treatment of Mycobacterium Marinum Cutaneous Infections." Expert Opinion on Pharmacotherapy. Volume 8, Issue 17, 2007