ARS | Publication request: Pathogenicity comparison of high and low virulent strains of Vibrio scophthalmi in olive flounder (Paralichthys olivaceus)

Submitted to: Fisheries Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 11, 2012
Publication Date: November 27, 2012
Citation: Qiao, G., Jang, I., Won, K., Woo, S., Xu, D., Park, S. 2012. Pathogenicity comparison of high and low virulent strains of Vibrio scophthalmi in olive flounder (Paralichthys olivaceus). Fisheries Sciences. 79:99-109.

Interpretive Summary: There is not information available on pathogenicity to olive flounder caused by different virulence strains of V. scophthalmi. In this study, the high and low virulent strains (HVS and LVS) were compared for the pathogenic characteristics, including adhesion and survival, superoxide dismutase (SOD) activity and extracellular products (ECP) of bacterial cells. The study also included cell-mediated defense of macrophages from olive flounder against V. scophthalmi infection in vitro. The results demonstrated some significant difference on pathogenic characteristics between two virulence strains. The HVS showed higher SOD activity, nitric oxide production and viable cell numbers in serum and skin mucus than LVS. These two stains of V. scophthalmi also induced various host immune responses. The macrophages of olive flounder demonstrated the lower extracellular O2- overflow and intracellular O2- concentration induced by the HVS than by LVS. These results will be benefit to fish health managers and producers for understanding pathogenic characteristics of the infected bacteria, preventing fish disease, and minimizing loss in aquaculture.

Technical Abstract: Vibrio scophthalmi is a bacterial pathogen of olive flounder (Paralichthys olivaceus) and virulence is different from various strains. There is not information available on pathogenicity to olive flounder caused by different strains of V. scophthalmi. In this study, the high and low virulent strains (HVS and LVS) were compared for the pathogenic characteristics, including adhesion and survival, superoxide dismutase (SOD) activity and extracellular products (ECP) of bacterial cells. The study also included cell-mediated defense of macrophages from olive flounder against V. scophthalmi infection in vitro. The results demonstrated that SOD activity of HVS was higher than LVS. Viable cell number of HVS in serum increased by 2 log unit at 18 h, whereas LVS decreased. Cell number of HVS in skin mucus increased significantly and LVS maintained invariable numbers. LD50 values of HVS and LVS ECP to olive flounder were 10.14 and 15.99 µg/g fish, respectively. ECP showed positive to naphtol-AS-BI-phosphohydrolase, lipase, gelatinase and leucine arylamidase. The phagocytosis test showed both HVS and LVS could be ingested without significant difference. The extracellular O2- overflow and intracellular O2- concentration of macrophages induced by HVS was lower than by LVS. Nitric oxide production was significantly higher by HVS than by LVS.