Mycobacterium marinum Infection in a 33-Year-Old Man

One week after redness and swelling arose on the left second finger, a 33-year-old man sought medical evaluation. He reported some tenderness and difficulty in flexing the digit but could not recall injuring the finger. The medical history included treatment of seborrheic dermatitis and acne.

A tender, swollen, mildly erythematous proximal interphalangeal joint of the left second finger was noted. No evidence of trauma was seen. The initial differential diagnosis included bursitis and septic arthritis; azithromycin was prescribed.

Following 2 weeks of unsuccessful treatment, the patient was reevaluated. Increased swelling, tenderness, some draining, erythema, and slight crusting were observed. An incision was made; however, the area did not drain. The patient was referred for wound culture and debridement.

The affected area was debrided, specimens were collected for pathologic examination, and cultures were obtained for aerobic and anaerobic bacteria. The patient was given broad-spectrum oral antibiotics pending culture results, which were negative. Debrided material showed granulation tissue. Stains for acid-fast bacilli were negative.

A culture specific for Mycobacteria marinum grew out the organism. The patient later recalled that about 1 month before the symptoms arose, he had scraped his finger on a barnacle while working on his boat.

Dr Jonathan S. Crane and John D. Schoonmaker, PA-C, of Wilmington, NC, write that a negative acid-fast bacillus stain from one area of a joint does not always rule out the presence of a mycobacterium. Therefore, specific cultures for these organisms are warranted for a septic finger joint. In patients with chronic erythematous draining areas, test for bacterial infections, including those caused by atypical mycobacteria, fungal infections, and cancer.

Clarithromycin, rifampin, and ethambutol were prescribed for this M marinum infection. Diarrhea developed and was traced to the rifampin, which was discontinued. Despite 5 months of therapy with the 2 remaining agents, the infection failed to resolve. Doxycycline and ciprofloxacin were added to the regimen; therapy was continued for another 6 months and cured the infection.