The virulence of 5 Streptococcus iniae stains against healthy flounder(Paralichthys olivaceus)was tested through challenge experiment.The results showed that LD50 of strain NUF849,NUF812,NUF701,NUF693 and NUF633was 3.0×105,1.1×106,4.2×107,1.2×107and 2.4×107CFU/mL,respectively.The extracellular products(ECPs)of the five stains of S.iniae were obtained using cellophane plate culture technique with their protein composition profiled through SDS-PAGE.Eight distinct bands with molecular weight(MW)of 14,20,27,30,...