Submitted to: Catfish Farmers of America Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2003
Publication Date: February 21, 2003
Citation: ARIAS, C.R., SHOEMAKER, C.A., EVANS, J.J., KLESIUS, P.H. A COMPARATIVE STUDY OF EDWARDSIELLA ICTALURI PARENT (ELIO) AND EDWARDSIELLA ICTULARI RIFAMPICIN-MUTANT (RE-33) ISOLATES. CATFISH FARMERS OF AMERICA RESEARCH SYMPOSIUM. 2003. Technical Abstract: Edwardsiella ictaluri is the causal agent of the enteric septicemia of catfish (ESC). This disease constitutes a major problem for the catfish industry being responsible for more than 20 million dollars per year. Efforts to control ESC lead to the development of a modified live vaccine by Klesius and Shoemaker in 1999. They obtained this modified strain (RE-33) by rifampicin-resistant selection of the parent strain EILO. RE-33 is unable to cause ESC but it does stimulate protective immunity in catfish. This modified live ESC vaccine is marketed by Intervet under the label of AQUAVAC-ESC® as a licensed vaccine administered by immersion of 7 to 10 day post hatch channel catfish. Preliminary characterization of this mutant associated its avirulent phenotype to the lack of an O-side chain LPS. The increasing use of AQUAVAC-ESC® throughout the catfish industry warrants a further comparative study between the wild type and the RE-33 mutant. The objectives of this work were to extensively characterize RE-33 strain and to find characteristics that could be used to discriminate between the RE-33 and its parent isolate, EILO. Electrophoretic analysis of lipopolysaccharides (LPS) patterns showed high homology between both isolates. Further characterization of LPS by immunoblotting revealed main differences in LPS composition. The RE-33 isolate lacks the high molecular weight bands of the LPS (HMW-LPS). Outer membrane protein (OMP) analysis also showed some immunological differences between RE-33 and EILO parent strain. Only two fingerprinting techniques, fatty acid composition analysis and Biolog phenotypic profiles, were able to discriminate between both isolates.