Detection of a new Mycobacterium species in wild striped bass in the Chesapeake Bay

Investigation into recent declines in striped bass health in the Chesapeake Bay in Maryland resulted In the isolation of a putative new species of Myc obacterium. This isolate was obtained from fish showing skin ulcers and int ernal granulomas in various organs. The isolate was slow growing at 28 degr eesC; was nonchromogenic; showed no activities of nitrate reduction, catala se activity, Tween 80 hydrolysis, tellurite reduction, or arylsulfatase red uction; grew best at low salt concentrations; and was urease and pyrazinami dase positive. By PCR a unique insertional sequence was identified which ma tched nothing in any database. Analysis of the nearly complete 16S rRNA gen e sequence also indicated a unique sequence which had 87.7% sequence homolo gy 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. These data support the conc lusion that the isolate probably represents a new mycobacterial species.