Issue: May 2006
Just a Scratch . . .

Norman A. Poulsen, M.D.

A quick brush with barnacles while cleaning your prop could lead to months of treatment for a rare infection.  –by Norm Poulsen

I have been sailing on the Bay for just about as long as I have been a family physician – more than 25 years now – and nearly all my encounters with the Chesapeake have been enjoyable. That changed on a fine Saturday afternoon last August, however, when I had a brush with one of the strains of bacteria that researchers now suspect are a threat to the Bay’s rockfish. Luckily, they are far less dangerous to humans.

My wife Chris and I had anchored our sailboat Blue Moon in Eagle Cove at the northern end of Gibson Island, planning to relax in the cockpit for a few hours, eat dinner and then head back in to the dock. First, though, I was going to go under the boat to clean the propeller and its shaft of the barnacles and other marine crud that I knew would be growing there. I gathered together my diving mask, leather gloves, putty knife and Scotch-Brite pad. As I climbed down the swim ladder, I did not suspect that this simple and routine activity would affect me for the next several months.

After the usual six dives to clean the prop, I moved forward to attack the shaft. While scraping it off, I lightly brushed my bare arm against a couple of barnacles still clinging to the strut. I surfaced and checked my arm to find only two very faint scratches, with almost no bleeding. I took a few more minutes to finish cleaning the shaft, climbed back onboard, thoroughly washed the scratches with detergent and water and squeezed some antibiotic ointment on them. This was hardly the first time I’d had a cut exposed to Bay water, and I’d never suffered any long-term effects. But being a victim of knowing a little too much, I wondered at the time if I might get an infection in my arm.

I was concerned about two very different bacteria. One can be very aggressive and progress rapidly to a serious systemic infection and even death if not treated quickly. Even the name sounds bad: Vibrio vulnificus. It is found in up to 80 percent of Bay water samples taken in warm months and grows rapidly. It causes nausea, vomiting and diarrhea if sufficient amounts are ingested with raw seafood – especially oysters – and it can cause rapidly developing skin infections in wounds exposed to contaminated water. Most infections are mild, but even they can also lead to tissue destruction and large blister formation. In higher-risk individuals – people with liver disease or depressed immune systems, as well as chronic diseases like diabetes or rheumatoid arthritis – severe infections, sepsis and shock are possible, with death rates of approximately 50 percent. Luckily, significant infections are very rare. Awareness and prompt treatment of possible infections are the best prevention of serious problems. High-risk individuals should avoid exposing wounds to Bay water and might want to avoid eating raw shellfish (although there have been no recorded instances of illness from ingested Vibrio from shellfish harvested from the Chesapeake Bay). As I was not among the high-risk groups, however, I was not too worried about Vibrio. (And when I didn’t get sick and die within the next few days, I knew I was pretty much in the clear.)

The second type of infection I thought about is caused by a very slow-growing bacterium, Mycobacterium marinum, a close cousin to the bacteria that cause tuberculosis. Mycobacterium marinum grows in fresh, brackish or salt water, and even in fish tanks. The infection it causes among humans is known as "fish handler’s disease" or "fish-tank finger." It grows best at 28 to 32 degrees centigrade (82 to 90 degrees Fahrenheit.) When my scratches healed quickly, and my arm looked fine, I felt relieved.

Two weeks later, however, I noticed a small reddish-purple bump where one of the scratches had been. Exercising my excellent capacity for denial, I was able to ignore it. Over the next two weeks, several more bumps developed, although the entire involved area was still less than an inch in size. It didn’t hurt much and didn’t itch, and it was easy to dismiss as insignificant. But then I noticed a tender, swollen lymph node just above my elbow, and a few of the bumps started to drain. I could no longer persuade myself that this was nothing. I called my primary-care physician’s office and told the receptionist that I believed I had a Mycobacterium marinum infection in my arm. After a moment’s silence, she said, "I am going to have the triage nurse talk to you." I told the same thing to the nurse, and after the same moment’s silence, she told me that I had to come right in. I replied that I had had the infection for a few weeks already, and did they have an appointment next Monday?

When I saw my physician, she took my word for what I had, cultured the drainage and started me on clarithromycin (Biaxin). Two and a half months of antibiotics later, the lesions were smaller and fading, but still present. Meanwhile, five weeks after my doctor’s visit, I received a call that the culture was positive for Mycobacterium, though it had still not been identified as to which type.

According to the medical literature, Mycobacterium marinum infections are quite rare, and many physicians even in the Chesapeake Bay area are not aware of this type of infection. Since I contracted mine, however, I have found that four of my sailing friends have had the same thing. One didn’t treat it at all, and it cleared up on its own after about a year and a half; two others took antibiotics for four months (as I expect to do), and one needed surgery and nine months of antibiotic treatment. They all got the infection from cuts or abrasions that occurred underwater, which seems to be characteristic of this problem. None resulted from a previous cut that was later exposed to the Bay.

I have seen a number of accounts in the medical literature about patients who underwent multiple cultures and biopsies to try to diagnose the infection, with a resultant delay in proper treatment. These bacteria do not like humans’ normal 98-degree core body temperature – which makes it less of a threat, because the infection stays confined to the cooler extremities and does not become systemic. But that same characteristic makes it difficult to identify in a laboratory, where most bacterial cultures are grown at body temperature. LabCorp, one of the nation’s largest laboratories, wasn’t quite sure what to do with the specimen from my arm that we sent in. An ordinary wound culture, which is usually complete within a few days, would have been reported as negative after no bacteria had grown from my sample. Once a physician is familiar with these infections, however, a culture is not always needed to make the diagnosis.

Just because the infection is slow-growing does not mean that it is harmless. If it gets into the joints or tendons, especially in the fingers, it can be destructive and may need surgical excision in addition to antibiotics. Antibiotic therapy is lengthy, and several different treatments are available. It appears that the one I am taking (Biaxin) is the most widely used, but sometimes several medications must be prescribed simultaneously, including rifampin and ethambutol, two drugs usually reserved to treat tuberculosis. A Mycobacterium marinum infection will often turn up a positive result on a PPD skin test (the one used to diagnose exposure to TB). Mine did; if I had not known the reason, I would have needed to take six to nine months of treatment with an anti-TB drug, isoniazid. Ironically, isoniazid does not treat Mycobacterium marinum, and it would not have helped my infection.

So, if you get a cut while you are in contact with Bay water that initially heals, but a few weeks later the site develops a non-painful, non-itchy, reddish-purple bumpy rash that doesn’t go away, don’t ignore it. Go see your physician, armed now with a little bit of knowledge. The best prevention is to avoid underwater cuts; wear gloves and a heavy shirt when cleaning boat bottoms – and don’t kick barnacle-covered pilings with bare feet!

Norman A. Poulsen, M.D., is chief of the family practice department for Johns Hopkins Community Physicians and practices in Odenton, Md. He sails his Hylas 44, Blue Moon, out of Cornfield Creek off the Magothy River.


A First-Aid Kit to Keep Aboard

These suggested contents for a fairly minimal first-aid kit can be packed into a Tupperware or similar container and kept aboard a boat.

        Two pairs of vinyl or latex gloves

        One box of assorted adhesive bandages

        Six 2- or 4-inch sterile gauze pads

        Four 2-inch non-stick gauze pads

        One roll of conforming roller gauze(Kling or Curlex)

        One roll of 1-inch-wide adhesive cloth tape

        One box of alcohol pads (to wipe area around

                 wound so adhesive tape will stick)

        One 3-inch-wide stretch wrap (e.g., Ace)

        One bottle Povidone-iodine cleaning solution

                 (or pre-packaged swabs)

        One tube of triple antibiotic cream

                 (e.g., Neosporin)

        Supply of acetominophen (e.g., Tylenol)

        Supply of anti-motion sickness medication

                 (e.g., Dramamine or Bonine)

        One pair of small tweezers

        One pair of wire cutters

        One pair of needle-nose pliers

Here are two first-aid manuals which look reasonable for this purpose, both available at for the indicated prices:

FastAct Pocket First Aid Guide, $5.95; American College of Emergency Physicians First Aid Manual, $10.20. – N.P.