Mycobacterium shottsii sp nov., a slowly growing species isolated from Chesapeake Bay striped bass (Morone saxatilis)

Slowly growing, non-pigmented mycobacteria were isolated from striped bass (Morone saxatilis) during an epizootic of mycobacteriosis in the Chesapeake Bay. Growth characteristics, acid-fastness and results of 16S rRNA gene sequencing were consistent with those of the genus Mycobacterium. A unique profile of biochemical reactions was observed among the 21 isolates. A single cluster of eight peaks identified by analysis of mycolic acids (HPLC) resembled those of reference patterns but differed in peak elution times from profiles of reference species of the Mycobacterium tuberculosis complex. One isolate (M175(T)) was placed within the slowly growing mycobacteria by analysis of aligned 16S rRNA gene sequences and was proximate in phylogeny to Mycobacterium ulcerans and Mycobacterium marinum. However, distinct nucleoticle differences were detected in the 16S rRNA gene sequence among M175(T), M. ulcerans and M. marinum (99-2% similarity). Isolate IM175(T) could be differentiated from other slowly growing, nonpigmented mycobacteria by its inability to grow at 37degreesC, production of niacin and urease, absence of nitrate reductase and resistance to isoniazid (1 mug ml(-1)), thiacetazone and thiophene-2-carboxylic hydrazide. Based upon these genetic and phenotypic differences, isolate IM175T (= ATCC 700981(T) = NCTC 13215(T)) is proposed as the type strain of a novel species, Mycobacterium shottsii sp. nov.