Detection And Characterization Of A New Mycobacterium Species In Wild Striped Bass From The Chesapeake Bay     Elankumaran, S1, Robert A. Heckert1, John Jacobs2, Rauf Ahmed1, Brett Coakley3, Craig Weedon3, Larry Pieper3, Karl Roscher4, Cindy Driscoll3, Charles Poukish5 and Ana Baya1   1Virginia-Maryland Regional College of Veterinary Medicine, Maryland Campus. 2University of Maryland, Center for Environmental Science, Cambridge, Maryland. Maryland Department of Natural Resources, 4Maryland Department of Agriculture and 5Maryland Department of the Environment   In 1994,the striped bass population in the Chesapeake Bay experienced a disease problem manifested as cutaneous ulcers. A putative new species of Mycobacterium was isolated from fish showing skin ulcers and granulomas in various organs. Similar isolates were recovered from other sick fish over the following years. The isolate grew slowly at 28C; was non chromogenic; showed no activities of nitrate reduction, catalase activity, Tween80 hydrolysis, tellurite reduction or arylsulfate reduction; grew best at low salt concentrations; and was urease and pyrazinamidase positive. A unique insertion sequence was identified By PCR did not match anything in genetic databases. Analysis of the nearly complete 16S rRNA gene sequence also indicated a unique sequence that had a 87.7% sequence homology to Mycobacterium ulcerans, 87.6% homology to Mycobacterium tuberculosis and 85.9% homology to Mycobacterium marinum. Phylogenetic analysis placed the organism close to the tuberculosis complex. Results of the biochemical and genetic analysis strongly suggested that this isolate may be a new species of Mycobacterium. This new isolate was inoculated into susceptible striped bass and the bacterium was recovered and identified. It was also recovered from sentinel striped bass placed in contact with the experimentally inoculated fish.