Abstract

Edwardsiella ictaluri is a Gram-negative facultative intracellular pathogen causing enteric septicemia of channel catfish (ESC). The disease causes considerable economic losses in the commercial catfish industry in the United States. Although antibiotics are used as feed additive, vaccination is a better alternative for prevention of the disease. Here we report the development and characterization of novel live attenuated E. ictaluri mutants. To accomplish this, several tricarboxylic acid cycle (sdhC, mdh, and frdA) and one-carbon metabolism genes (gcvP and glyA) were deleted in wild type E. ictaluri strain 93-146 by allelic exchange. Following bioluminescence tagging of the E. ictaluri ?sdhC, ?mdh, ?frdA, ?gcvP, and ?glyA mutants, their dissemination, attenuation, and vaccine efficacy were determined in catfish fingerlings by in vivo imaging technology. Immunogenicity of each mutant was also determined in catfish fingerlings. Results indicated that all of the E. ictaluri mutants were attenuated significantly in catfish compared to the parent strain as evidenced by 2,265-fold average reduction in bioluminescence signal from all the mutants at 144 h post-infection. Catfish immunized with the E. ictaluri ?sdhC, ?mdh, ?frdA, and ?glyA mutants had 100% relative percent survival (RPS), while E. ictaluri ?gcvP vaccinated catfish had 31.23% RPS after re-challenge with the wild type E. ictaluri.

Publisher

Public Library of Science

DOI

10.1371/journal.pone.0065973

Publication Date

6-7-2013

College

College of Veterinary Medicine

Department

Department of Basic Sciences

Keywords

Animals, Bacterial, Bacterial: genetics, Carbon, Carbon: metabolism, Citric Acid Cycle, Citric Acid Cycle: genetics, Edwardsiella ictaluri, Edwardsiella ictaluri: genetics, Edwardsiella ictaluri: metabolism, Edwardsiella ictaluri: pathogenicity, Enterobacteriaceae Infections, Enterobacteriaceae Infections: immunology, Enterobacteriaceae Infections: microbiology, Enterobacteriaceae Infections: prevention & contro, Fish Diseases, Fish Diseases: immunology, Fish Diseases: microbiology, Fish Diseases: prevention & control, Genes, Genotype, Ictaluridae, Ictaluridae: immunology, Ictaluridae: microbiology, Immersion, Injections, Intraperitoneal, Luminescent Measurements, Sequence Deletion, Sequence Deletion: genetics, Survival Analysis, Vaccination, Virulence, Virulence: genetics

Disciplines

Veterinary Medicine

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