Isolation of Yersinia ruckeri Strain H01 from Farm-Raised Amur Sturgeon Acipenser schrencki in China

Yersinia ruckeri is the causative agent of enteric redmouth disease or yersiniosis, which affects salmonids and several other species of fish. However, there are no reports on the characteristics and pathogenicity of Y. ruckeri isolated from farm-raised Amur Sturgeon Acipenser schrencki. Here, we isolated and characterized Y. ruckeri strain H01 from the diseased Amur Sturgeon in China. The phenotypic and genotypic characteristics of Y. ruckeri were observed, and its virulence was tested by examining experimentally infected sturgeons. Examination of the flagellar morphology of Y. ruckeri by transmission electron microscopy showed five to eight peritrichous flagella located on the cell body. Actively dividing cells with an obvious cell membrane were approximately 0.64m in diameter and between 1.7 and 2.5m in length. The dose that was lethal to 50% of the test fish after intraperitoneal injection was determined to be 7.2x106 CFU, and Y. ruckeri could be reisolated from the liver and kidneys of infected sturgeon. Antimicrobial susceptibility tests showed that H01 was susceptible to 10 antimicrobial agents. Part of the 16S rRNA sequences (563 base pair) was amplified and sequenced to study the genotypic characterization in Y. ruckeri (GenBank accession number JQ657818). The phylogenetic tree revealed H01 was clustered together with Y. ruckeri strains. Together, this study describes the isolation, characterization, and phenotypicgenotypic analysis of a Y. ruckeri strain isolated from farm-raised Amur Sturgeon. The results discovered may provide some theoretical basis for the prevention and control of yersiniosis in Amur Sturgeon. Received July 23, 2012; accepted September 5, 2012