Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2008
Publication Date: 3/31/2008
Citation: Lafrentz, B.R., Lapatra, S.E., Call, D.R., Cain, K.D. 2008. Development and Characterization of Rifampicin Resistant Flavobacterium Psychrophilum Strains and Their Potential as Live Attenuated Vaccine Candidates. In: Proceedings of the Annual Eastern Fish Health Workshop, March 31 - April 4, 2008, Atlantic Beach, North Carolina. p. 49.
Technical Abstract: Previous studies have demonstrated that passage of pathogenic bacteria on increasing concentrations of the antibiotic rifampicin leads to the attenuation of virulence and these resistant strains may serve as live attenuated vaccines. Two rifampicin resistant strains of Flavobacterium psychrophilum, 259-93A.16 and 259-93B.17, were generated by routine passage on TYES plates containing increasing concentrations of rifampicin. Electrophoretic analysis of whole-cell lysates prepared from the parent and resistant strains identified numerous differences between the 259-93B.17 strain and parent strain, while there were no differences identified between the 259-93A.17 and parent strains. The LPS banding patterns were identical between all three strains. Bacterial challenges of rainbow trout (Oncorhynchus mykiss Walbaum) with the resistant strains demonstrated attenuation of the 259-93B.17 strain and reduced virulence of the 259-93A.16 strain at the challenge doses tested. Immunization of rainbow trout with the attenuated live 259-93B.17 strain by intraperitoneal injection and immersion resulted in significant protection against challenge with the virulent parent F. psychrophilum strain and fish exhibited elevated specific antibody titers. The results demonstrate that the attenuated 259-93B.17 strain may serve as an effective live vaccine for the prevention of F. psychrophilum infections.