Detection of antibody in rainbow trout against Aeromonas salmonicida by enzyme-linked immunosorbent assay.

Abstract

An enzyme-linked immunosorbent assay (ELISA) was developed to detect anti-Aeromonas salmonicida antibody in rainbow trout immunized with the formalin-killed bacteria. Absorbance of the sera in ELISA correlated well with the serum dilutions and the agglutinin titer of each serum. The ELISA titers of the sera were much higher (usually 5 to 40 times) than the titers determined by agglutination test. By ELISA, antibody was detected in 1 out of 4 fish 2 weeks after immunization and in all of the fish 4 weeks after immunization. On the other hand, agglutinin was first detected 4 weeks after immunization. Inoculation of casein into fish before immunization showed immunostimulating effect on antibody production. The ELISA did not detect antibodies against A. hydrophila, A. punctata, A. liquefaciens, Vibrio anguillarum and other species of Vibrio in rainbow trout, whereas extensive cross reactions were observed among these bacteria and A. salmonicida by agglutination test and immunodiffusion.