Note Mycobacterium shottsii sp. nov., a slowly growing species isolated from Chesapeake Bay striped bass (Morone saxatilis) Martha W. Rhodes, 1 Howard Kator, 1 Shaban Kotob, 1 Peter van Berkum, 2 Ilsa Kaattari, 1 Wolfgang Vogelbein, 1 Frederick Quinn, 3 Margaret M. Floyd, 3 W. Ray Butler 3 and Christopher A. Ottinger 4 Correspondence Martha W. Rhodes martha@vims.edu 1 Virginia Institute of Marine Science, College of William and Mary, PO Box 1346, Gloucester Point, VA 23062, USA 2 United States Department of Agriculture, Beltsville, MD, USA 3 Tuberculosis/Mycobacteriology Branch, Centers for Disease Control and Prevention, Atlanta, GA, USA 4 US Geological Survey, Leetown Science Center, National Fish Health Research Laboratory, Kearneysville, WV, USA 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 nucleotide differences were detected in the 16S rRNA gene sequence among M175 T , M. ulcerans and M. marinum (99?2 % similarity). Isolate M175 T could be differentiated from other slowly growing, non- pigmented mycobacteria by its inability to grow at 37 ˚ C, production of niacin and urease, absence of nitrate reductase and resistance to isoniazid (1 mg ml 21 ), thiacetazone and thiophene-2- carboxylic hydrazide. Based upon these genetic and phenotypic differences, isolate M175 T (=ATCC 700981 T =NCTC 13215 T ) is proposed as the type strain of a novel species, Mycobacterium shottsii sp. nov. Mycobacteria are widely distributed in both fresh and marine waters and include species pathogenic to marine animals and humans (Collins et al., 1984; Falkinham, 1996; Dailloux et al., 1999). An increased awareness of the diversity and complexity within the genus has resulted from the application of molecular techniques to the analysis of isolates from environmental sources and clinical speci- mens (Springer et al., 1993). During a recent epizootic of mycobacteriosis in striped bass, Morone saxatilis, from the Chesapeake Bay, various mycobacteria were isolated including a homogeneous group that, on the basis of traditional biochemical tests, mycolic acid analyses and a distinct 16S rRNA gene sequence, could not be assigned to any recognized species (Rhodes et al., 2001). More extensive characterization using additional biochemical tests, antimicrobial susceptibility and HPLC mycolic acid pattern analysis of additional isolates indicated that these isolates belong to a novel taxon. In this report, we describe the results of a taxonomic study of these isolates and propose that they are representative of a novel species, Mycobacterium shottsii sp. nov. Isolate M175 T and 20 similar isolates were recovered from granulomatous lesions in striped bass (Rhodes et al., 2001). One isolate each (M23 and M216) was recovered from kidney and skin lesions and all others were from the spleen. Additional isolates included M115, M120, M121, M148, M177, M179, M182, M200, M202, M203, M205, M208, M210, M211 and M217–M220. Growth and biochemical testing included reference strains of Mycobacterium avium Published online ahead of print on 16 August 2002 as DOI 10.1099/ ijs.0.02299-0. The GenBank accession number for the 16S rRNA sequence of Mycobacterium shottsii M175 T is AY005147. 02299 G 2003 IUMS Printed in Great Britain 421 International Journal of Systematic and Evolutionary Microbiology (2003), 53, 421–424 DOI 10.1099/ijs.0.02299-0