DAO 79:107-118 (2008)  -  doi:10.3354/dao01891

Biochemical, molecular, and virulence characteristics of select Mycobacterium marinum isolates in hybrid striped bass Morone chrysops × M. saxatilis and zebrafish Danio rerio

V. E. Ostland1,*, V. Watral2, C. M. Whipps2, F. W. Austin3, S. St-Hilaire4, M. E. Westerman1, M. L. Kent2

1Kent SeaTech Corporation, 11125 Flintkote Ave, Suite J, San Diego, California 92121, USA
2Center for Fish Disease Research, Department of Microbiology, 220 Nash Hall, Oregon State University, Corvallis, Oregon 97331-3804, USA
3Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Starkville, Mississippi 39762-6100, USA
4Department of Biological Sciences, Idaho State University, Pocatello, Idaho 83209, USA

ABSTRACT: A panel of 15 Mycobacterium marinum isolates was characterized by biochemical tests, sequencing the ribosomal DNA intergenic spacer (ITS) region and the heat shock protein 65 gene (hsp65) and pulsed-field gel electrophoresis (PFGE). The biochemical characteristics of all isolates were similar, except for Tween 80 hydrolysis. DNA sequence of hsp65 for a subset of isolates were identical; however, at position 5 of the ITS rDNA, a single nucleotide polymorphism was identified. Isolates possessing a guanine residue at this position (G strains) were unable to hydrolyze Tween 80, while isolates that contained an adenine residue at this position (A strains) were positive for Tween 80 hydrolysis. PFGE successfully discriminated between the G and A strains; all G strains had identical AseI restriction enzyme-cutting patterns while the A strains exhibited a variety of cutting patterns. Eight isolates (4 G and 4 A strains) were further characterized for virulence by experimental infection of hybrid striped bass (HSB) Morone chrysops × M. saxatilis and zebrafish Danio rerio. Seven of the 8 strains produced cumulative mortality ranging from 13.3 to 83.3% in the HSB virulence trial. The M. marinum reference strain ATCC 927T did not produce mortality in HSB. HSB exposed to the G strains had significantly higher cumulative mortality than those exposed to the A strains. When these same isolates were tested in zebrafish, 6 of the 8 strains caused 100% cumulative mortality, with 2 of the A strains being the most pathogenic. In zebrafish, however, ATCC 927T was virulent and produced 28.5% mortality. Collectively, we conclude that the M. marinum G strains are unique and may represent a distinct virulence phenotype in HSB, but this trend was not consistent in zebrafish.


KEY WORDS: Mycobacterium marinum · Hybrid striped bass · Zebrafish · Mycobacteriosis ·Virulence


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Cite this article as: Ostland VE, Watral V, Whipps CM, Austin FW, St-Hilaire S, Westerman ME, Kent ML (2008) Biochemical, molecular, and virulence characteristics of select Mycobacterium marinum isolates in hybrid striped bass Morone chrysops × M. saxatilis and zebrafish Danio rerio. Dis Aquat Org 79:107-118

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