An assessment of the antigenic homogeneity of Edwardsiella ictaluri using monoclonal antibody

Monoclonal antibodies were made against the reference strain of Edwardsiella ictaluri (ATCC 3320). Antibody produced by one of seven anti‐ E. ictaluri hybridomas reacted positively by the immunofluorescent antibody technique against 17 other E. ictaluri isolates. All hybridoma antibodies failed to react with six other bacterial species pathogenic to fish including E. tarda . Ouchterlony tests indicated that four anti‐ E. ictaluri clones produced only one kind of immunoglobulin. Electrophoresis of 14 different E. ictaluri isolates indicated identical protein bands at 36 and 60 kilodaltons (KD) in all isolates except an isolate from Thailand. Using the immunoblot method, channel catfish anti‐ E. ictaluri serum reacted with protein bands at 34 and 60 KD, which indicates that this molecular weight protein in the bacterium may be the dominant immunoprotein.