Mycobacterium marinum skin infections. Report of 31 cases and review of the literature

BACKGROUND: Mycobacterium marinum is a rare cause of skin infections, and its treatment has been based primarily on the personal experience and preferences of individual investigators without the benefit of large studies. METHODS: Thirty-one patients with confirmed M marinum infection were identified at 33 Kaiser Permanente Northern California Region medical centers by microbiologic records, and their charts were reviewed. RESULTS: The upper extremity was affected in 90% of cases, and lymphatic or local spread was seen during the initial examination or during observation in 25 patients (81%). Granuloma was present in 22 (63%) of 35 biopsy specimens, and staining for acid-fast bacteria yielded positive results in two of 22 specimens. Cure or improvement occurred in 22 (81%) of 27 patients in whom outcome could be evaluated. Treatment with ethambutol plus rifampin appeared more successful (effective in five [100%] of five cases) than minocycline treatment (effective in 10 [71%] of 14 cases), although not significantly so (P = .28). Adverse reactions, most of which were gastrointestinal, occurred in five patients (18%). CONCLUSION: Ethambutol plus rifampin appears more useful than minocycline in treating cutaneous M marinum infection. This result remains to be confirmed by larger clinical studies, which may be difficult because this infection is relatively rare.