title: Functional genomics approach to the identification of virulence genes involved in Edwardsiella tarda pathogenesis.
abstract: Edwardsiella tarda is an important cause of hemorrhagic septicemia in fish and also of gastro- and extraintestinal infections in humans. Here, we report the identification of 14 virulence genes of pathogenic E. tarda that are essential for disseminated infection, via a genome-wide analysis. We screened 490 alkaline phosphatase fusion mutants from a library of 450,000 TnphoA transconjugants derived from strain PPD130/91, using fish as an infection model. Compared to the wild type, 15 mutants showed significant decreases in virulence. Six mutants had insertions in the known virulence-related genes, namely, fimA, gadB, katB, pstS, pstC, and ssrB. Some mutants corresponded to known genes (astA, isor, and ompS2) that had not been previously shown to be involved in pathogenesis, and three had insertions in two novel genes. In vivo infection kinetics experiments confirmed the inability of these attenuated mutants to proliferate and cause fatal infection in fish. Screening for the presence of the above-described virulence genes in six virulent and seven avirulent strains of E. tarda indicated that seven of the genes were specific to pathogenic E. tarda. The genes identified here may be used to develop vaccines and diagnostic kits as well as for further studying the pathogenesis of E. tarda and other pathogenic bacteria.
authors.affiliation: Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore 117543, Singapore.
authors.forename: Putanae S
authors.initials: PS
authors.lastname: Srinivasa Rao
authors.forename: Tit Meng
authors.initials: TM
authors.lastname: Lim
authors.forename: Ka Yin
authors.initials: KY
authors.lastname: Leung
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D015139:Blotting, Southern; D003001:Cloning, Molecular; D020609:Edwardsiella tarda / Q000235:genetics* / Q000472:pathogenicity*; D005399:Fishes; D016680:Genome, Bacterial; D007928:Lethal Dose 50; D009154:Mutation; D009876:Operon; D014774:Virulence / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins