Pathogenicity of Streptococcus parauberis to Olive Flounder Paralichthys olivaceus

摘要

Streptococcus parauberis (stain SNUFPC-050803), isolated from diseased olive flounder Paralichthys olivaceus in Jeju Island, Korea, was evaluated for its patho-genicity to healthy juvenile flounder (29.3 g in average body weight). When challenged withthe isolate by intraperito-neal injection with tenfold serial dilutions of 4.5 x 10 - 10~6 CFU/fish, the cumulative mortality ranged from 10% to 80% within 14 days except for 4.5 x 10 CFU/fish and control with no mortality. Disease signs were hemorrhagearound the mouth, eyes and pectoral fins, pale and friable liver with hepatomegaly and ascitic fluid in the peritoneal cavity. These signs were similar to those of naturally affected fish. S. parauberis was reisolated and identified by PCR method, whichconfirmed the pathogenicity of the bacterium to olive flounder.