Immunogenicity of formalin-killed cells of Edwardsiella tarda grown in Mg super(2+) and Fe super(2+)-deficient media

Edwardsiellosis causes serious damage to aquaculture industries of Japanese flounder, Paralichthys olivaceus, and red sea bream, Pagrus major, in Japan. To date effective vaccines for this disease have not been developed. In this study efficacies of bacterins (formalin-killed cells) of Edwardsiella tarda grown in metal ion-deficient, Fe super(2+)-deficient, Mg super(2+)-deficient or H sub(2)O sub(2)-supplemented media were investigated in flounder in comparison with a control bacterin prepared from the bacterial cells grown in yeast extract medium by immersion-challenged with E. tarda after two weeks post-vaccination. As a result, although survival rates of all experimental groups at a month post-challenge were higher than that of the non-vaccinated group, none of the cultural conditions remarkably improved the efficacy of the control bacterin in respect of survival rate as well as carrier rate of survivors.