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.