Phenotypic and Genomic Characterization of Vibrio rotiferianus Isolated From Starry Flounder ( Pl

ABSTRACT

Vibrio rotiferianus is a bacterial species associated with mortality in various marine organisms. This bacterium has previously been isolated from olive flounder ( Paralichthys olivaceus ) farms in the Republic of Korea. However, studies on pathogens associated with starry flounder ( Platichthys stellatus ) remain limited. In the present study, V. rotiferianus isolates obtained from starry flounder were characterized using phenotypic and genomic analyses. Species identification was confirmed by rpoD phylogenetic analysis and multilocus sequence analysis (MLSA) based on the concatenated gyrA , gyrB , recA , and dnaJ gene sequences, which is an important molecular marker for accurate species discrimination within the Vibrio harveyi clade. Even among strains obtained from the same aquaculture site, variations in antimicrobial susceptibility and thiosulfate–citrate–bile salts–sucrose growth characteristics were observed. To evaluate the association between this pathogen and mass mortality events in starry flounder in the Republic of Korea, an experimental challenge was conducted using an intraperitoneal injection of V. rotiferianus BD182406. No mortality or clinical signs were observed following intraperitoneal challenge with strain BD182406, indicating that this isolate was not pathogenic to starry flounder under the experimental conditions used in this study. These findings suggest that additional studies using multiple V. rotiferianus isolates and alternative infection models are required to clarify the pathogenic potential of this species in starry flounder.