Background: Mycobacterium marinum is a nontuberculous mycobacterium responsible for skin infections. Although cases have been seldom reported, no series of M marinum infection has been recently reported and the treatment is not standardized.

Methods: A national survey was conducted on culture-confirmed M marinum infections that occurred in France from January 1, 1996, to December 31, 1998. Clinical characteristics and therapeutic data were analyzed, and the minimum inhibitory concentrations of 11 antibiotics were determined against the causative isolates.

Results: Sixty-three cases of M marinum infection were studied. In 53 (84%) of the patients, inoculation was related to fish tank exposure. The site of infection was mainly the upper limb (in 60 [95%] of the 63 patients), and infection was spread to deeper structures in 18 (29%) of the patients. All patients were treated with antibiotics (median time, 3(1/2) months), and 30 (48%) underwent surgery. Various antibiotic regimens were prescribed, and the initial regimen was modified in 22 (35%) of the patients. Clarithromycin, cyclines, and rifampin were the most commonly prescribed antibiotics. Cure was observed for 55 (87%) of the patients. Failure was related to deep structure involvement (3 of 45 vs 5 of 18 patients; P =.04) but not to any antibiotic regimen. All strains showed the same susceptibility pattern without acquired resistance. The 90% minimum inhibitory concentrations of rifampin and rifabutin were far lower (0.5 and 0.06 micro g/mL, respectively) than the 90% minimum inhibitory concentrations of clarithromycin (2 micro g/mL) and the cyclines (minocycline, 4 micro g/mL; and doxycycline, 8 micro g/mL).

Conclusions: Mycobacterium marinum infections are emerging infections related to fish tank hobby. Because of the severity of the cases with spread of infection, clinical awareness of M marinum infection and its associated risk factors is important so that the diagnosis can be made and therapy can be initiated promptly.