Category Archives: Mycobacterium Marinum

Mycobacterium Marinum: an Unpleasant Bacterial Infection

Two friends – both retired and both long-time boaters – have recently encountered a little known and extremely unpleasant bacterial infection called “Mycobacterium Marinum,” or “M. Marinum.”  Following is their “story,” for awareness.

M. Marinum infection has several “street names,” including “fish tank granuloma,” “fish-handlers’ nodules,” “surfers’ nodules” and “waterman’s disease.”  M. Marinum is a rarely-occurring infection in humans, but medical diagnosis can be difficult.  One affected friend spends half of his year in Arizona and half his year cruising the US East Coast.  The other lives in suburban Maryland and enjoys recreational skin diving.  Both victims regularly participate in in-water boat maintenance and recreational activities, and neither is actually sure how or when they were infected.  In both cases, diagnosis of their M. Marinum was long delayed, with several mis-diagnoses by physicians along the way.  In both cases, the delays in diagnosis resulted in well established infection, required extensive surgical remediation, and risked the real possibility of limb amputation, or worse.  In one of these case, delayed correct diagnosis resulted in extensive hospital time, antibiotic-induced kidney failure, and necessitated kidney transplant.  As I said, an extremely unpleasant bacterial infection!

M. Marinum is found in fresh, brackish and salt water in various parts of the world.  It has been found in the Chesapeake Bay and other regional waters.  People who have breaks in the skin, such as cuts and scrapes, may be at risk:

•    when in contact with water from an aquarium or fish tank,
•    when handling, cleaning, or processing fish, or
•    while swimming or working in fresh or salt water.

M. Marinum infection is not spread from person to person. There is no evidence that human infections of M. Marinum occur if fresh or salt water is swallowed.

After exposure to the bacterium, symptoms usually appear within 2 to 4 weeks, however some reported cases have developed symptoms months later.  The most frequent symptom is localized discomfort with a slowly developing lump (nodule) at the site where the bacteria entered the body.  Frequently, the nodule is noticed on the hand or upper arm.  Late, the nodule can become an enlarging, oozing sore.  Swelling of nearby lymph nodes occurs.  This infection can also involve the joints and bones.  Serious complications involving internal organs is possible.  This occurs more commonly in immunocompromised individuals, such as those with AIDS, cancers, or are pregnant, or people taking immunosuppressive drugs such as steroids, chemotherapy, radiation, or immunosuppressive post-transplant medications. Infections with this bacterium can be treated with antibiotics.  Antibiotics may need to be taken for 6 months or more.

The delayed appearance of symptoms can make it hard to associate the onset of symptoms with water-based activity as the source of exposure.  Discomfort and swelling is frequently associated with more recent strenuous physical activity rather than long healed scratches. Therefore, correct diagnosis and effective antibiotic treatment can be seriously delayed. Common mis-diagnoses by physicians include fungal and parasitic infection, cellulitis, skin tuberculosis, rheumatoid arthritis, foreign body reaction, and skin tumor.  Delays in diagnosis can result in severely destructive infection.

M. Marinum is a gram positive rod, very closely related to the tuberculosis bacillus.  The definitive diagnosis for M. Marinum is a laboratory culture and DNA sequencing of the bacterium.  “Standard” lab culturing processes may lead to false negative conclusions.  A laboratory “Culture and Sensitivity” study for M. Marinum may take as long as 3 weeks of incubator time, and that at warmer temperatures, to produce reliable results.

Here’s what one affected victim wants us all to know about Mycobacterium Marinum;

“First, it’s not your ordinary bacteria, not even close.  As the surgeon put it, it’s a different animal altogether, more like TB than anything else.

“Second, it can be contracted through both salt and fresh water—and often through fish tank water!  What we know now is that fishermen and crabbers carry a bottle of bleach.  If they have a cut or scrape, they pour some bleach over it. Who knew?

“Third, this is not a deadly threat hanging over your head every time you take the boat out. Very few people actually get it.  But if something like this should happen to you–and your doctor can’t find a solution—tell him about the MTOA guy you know who contracted Mycobacterium Marinum.  Ask him to Google it. You might want to do that too.  We found a lot of information out there—once we knew what to look for!”

In closing, prevention is far better than correction.  Watermen who regularly handle fish, crabs, oysters, shrimp and other sea creatures routinely rinse their hands in a dilute mixture of household bleach and water.  “Bleach water” will kill the bacteria.  Routine use of antibacterial soap or bleach water is advisable for anyone working in aquatic environments.

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