Mycobacterium marinum with different responses to second-generation tetracyclines

BACKGROUND: Persistent cutaneous infections with Mycobacterium marinum can follow exposure of injured skin to contaminated water or fish, and can be treated with second-generation tetracyclines in addition to other antimicrobials. Due to the rarity of this infection, there are few data comparing the different treatment alternatives. METHODS: We report a patient with culture-proven M. marinum who was treated with two different second-generation tetracyclines. RESULTS: Our patient failed a 4-week trial of doxycycline, but responded rapidly to minocycline. CONCLUSION: This case suggests that, despite a similar mechanism, pharmacokinetics, and even sensitivity, these two agents may differ in their effectiveness against strains of M. marinum.