Mycobacterium marinum Infection Clinical Presentation

Updated: Jan 25, 2023
  • Author: Shirin A Mazumder, MD, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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M marinum infection often follows abrasions to an extremity occurring in nonchlorinated water. Fishermen, oyster workers, swimmers, and aquarium workers are predisposed to infection.

M marinum has an incubation period of approximately 2-3 weeks

A mildly tender papule or nodule initially appears at the site of trauma, slowly enlarges, and then suppurates or ulcerates.

The localized lesion can grow slowly over several months.

Localized pain and induration are common.

Further nodular lesions may develop along the lymphatic channels, resulting in ascending nodular lymphangitis.

Regional lymphadenitis and systemic symptoms are uncommon.

Contiguous spread to deeper structures (eg, tendons, joints, or even bones) occurs in up to one third of individuals with M marinum infection.



In individuals with M marinum infection, a papule or bluish nodule develops at the inoculation site. Suppuration or ulceration appears at a later stage.

An ascending nodular lymphangitis develops in 25-50% of infected patients. This entity also is seen in other infectious etiologies, especially sporotrichosis, New World cutaneous leishmaniasis, nocardiosis, ulceroglandular form of tularemia, infections with other nontuberculous mycobacteria (eg, Mycobacterium chelonae, Mycobacterium fortuitum, Mycobacterium kansasii), various fungal infections (blastomycosis, histoplasmosis, cryptococcosis, coccidioidomycosis) and several pyogenic bacteria (Staphylococcus aureus, Streptococcus pyogenes, Burkholderia pseudomallei, Bacillusanthracis).

An upper extremity is affected in nearly 90% of persons with M marinum infection, mostly on the hands. See the image below.

Photograph of Mycobacterium marinum infection. Photograph of Mycobacterium marinum infection.

Deeper involvement, with tenosynovitis, septic arthritis, and osteomyelitis of the underlying bone, may be evident on examination.

Most patients with M marinum infection have a tuberculin skin test result between 5-9 mm of induration.

M marinum infection may present similarly to interstitial granuloma annulare. [4]



Infection is caused by inoculation with M marinum. Individuals at an increased risk for infection include the following:

  • Fishermen and fish-processing workers

  • Saltwater aquarium maintenance personnel

  • Home aquarium owners

  • Immunocompromised individuals



Potential complications include the following:

  • Persistent ulceration or suppuration

  • Osteomyelitis

  • Tenosynovitis

  • Arthritis

  • Disseminated infection

  • Amputation of involved digit