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Isolation of rifampicin resistant Flavobacterium psychrophilum strains and their potential as live attenuated vaccine candidates

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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 passage on TYES plates containing increasing concentrations of rifampicin. Electrophoretic analysis of whole-cell lysates prepared fromthe parent and resistant strains identified five differentially expressed proteins between the 259-93B.17 strain and parent strain, while there were no differences identified between the 259-93A.16 and parent strain. The LPS banding patternswere identical between all three strains. Bacterial challenges of rainbow trout (Oncorhynchus mykiss Walbaum) with the resistant strains demonstrated that the 259-93B.17 strain was highly attenuated and the 259-93A.16 strain was modestly attenuated at the challenge doses tested. Immunization of rainbow trout with the live attenuated 259-93B.17 strain by intraperitoneal injection resulted in significant protection against challenge with the virulent parent F. psychrophilum strain at 8 and 15 weeks post-immunization and fish exhibited elevated specific antibody titers. Importantly, immersion delivery of the 259-93B.17 strain stimulated protective immune responses in fish at 10 weeks post-immunization. The results demonstrate that the rifampicin resistant 259-93B.17 strain may serve as an effective live attenuated vaccine for the prevention of F. psychrophilum infections.
Benjamin R. LaFrentz , Scott E. LaPatra , Douglas R. Call , Kenneth D. Cain
Flavobacterium psychrophilum , Oncorhynchus mykiss , animal pathogenic bacteria , antibiotic resistance , antibodies , bacterial infections , bacterial proteins , disease prevention , electrophoresis , fish , fish diseases , host-pathogen relationships , immune response , immunization , intraperitoneal injection , live vaccines , rifampicin , virulence
Vaccine 2008 10 16 v.26 no.44
Journal Articles, USDA Authors, Peer-Reviewed
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