What are the symptoms of Mycobacterium marinum infection?
Typically, patients may initially notice a small red bump or non-healing red sore on their skin a few weeks after a history of exposure to non-chlorinated water. Ninety percent of the cases involve the arms (upper extremities). They may remember getting a scratch, scrape, or puncture wound several weeks before while in the water. Many people may easily overlook the early signs and try over-the-counter antibiotic creams and disinfectants on their own in an attempt to make the bump or sore go away. Often, patients may not decide to go to their physician until they can't get rid of the bump for weeks or months, when they see more bumps, or when they see spreading bumps in a "line" pattern up their arm or leg.
Some patients may feel no pain or itch while others commonly have some localized pain and firmness at the site of the infection. Most otherwise healthy people overall feel well during the infection and do not have fever or chills.
Patients in poor health or those with other health issues like an impaired immune system or other serious illnesses may experience fever, enlarged localized lymph nodes, and systemic infection.
When M. marinum infects the skin, it causes localized microscopic nodules to form. These nodules are called granulomas. They occur at sites of skin trauma where there are scratches, cuts, and the like.
The granulomas slowly increase in size usually become visible within two to three weeks of exposure. Some reported cases have developed two to four months or more after exposure to M. marinum because of the very slow-growing nature of this bacterium.
The most frequent sign is a slowly developing nodule (raised bump) at the site the bacteria entered the body. Frequently, the nodule is on the hand or upper arm. Later the nodule can become an enlarging sore (an ulcer). Swelling of nearby lymph nodes occurs. Multiple granulomas may form in a line along the lymphatic vessel that drains the site. These lesions will usually spontaneously heal in several months. This infection can also involve the joints (septic arthritis) and bones (osteomyelitis).
A health-care provider should be consulted if a skin nodule or reddened sore (ulcer) develops following direct skin contact with fresh or saltwater or after handling or processing fish.
For people with compromise of the immune system, M. marinum infection can be especially serious and involve disseminated (widespread) disease. If an infection is suspected under such circumstances, a health-care provider should be promptly consulted.