Exposure history Exposure to aquatic animals 2023-12-30T09:25:04Z Mycobacterium marinum is an opportunistic pathogen inducing infection in fresh and marine water fish. Human infections with Mycobacterium marinum have been associated with the exposure of damaged skin to polluted water from fish pools or contacting objects contaminated with infected fish. Fish mycobacteriosis is clinically manifested and characterized in man by purple painless nodules, liable to develop into superficial crusting ulceration with scar formation. History of exposure to aquatic animals.