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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.

SUBMITTER: Srinivasa Rao PS

PROVIDER: S-EPMC148833 | biostudies-literature | 2003 Mar

REPOSITORIES: biostudies-literature

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Functional genomics approach to the identification of virulence genes involved in Edwardsiella tarda pathogenesis.

Srinivasa Rao Putanae S PS Lim Tit Meng TM Leung Ka Yin KY

Infection and immunity 20030301 3

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 show ...[more]

PMID: 12595451

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Project description:UnlabelledEdwardsiella tarda is an important pathogenic bacterium that can replicate in macrophages. However, how the intramacrophage infection process affects the virulence of this bacterium is essentially unknown. Here, we show that E. tarda replicates and induces a caspase-1-dependent cell pyroptosis in a murine macrophage model. Via pyroptosis, intracellular E. tarda escapes to the extracellular milieu, forming a unique bacterial population. Being different from the bacteria cultured alone, this unique population possesses a reprogrammed transcriptional profile, particularly with upregulated type III secretion system (T3SS)/T6SS cluster genes. Subsequent studies revealed that the macrophage-released population gains enhanced infectivity for host epithelial cells and increases resistance to multiple host defenses and hence displays significantly promoted virulence in vivo Further studies indicated that T3SS is essentially required for the macrophage infection process, while T6SS contributes to infection-induced bacterial virulence. Altogether, this work demonstrates that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, suggesting a positive role for intramacrophage infection in bacterial pathogenesis.ImportanceMany pathogens can replicate in macrophages, which is crucial for their pathogenesis. To survive in the macrophage cell, pathogens are likely to require fitness genes to counteract multiple host-killing mechanisms. Here, Edwardsiella tarda is proved to exit from macrophages during infection. This macrophage-released population displays a reprogrammed transcriptional profile with significantly upregulated type III secretion system (T3SS)/T6SS-related genes. Furthermore, both enhanced infectivity in epithelial cells and activated resistance to complex host defenses were conferred on this macrophage-primed population, which consequently promoted the full virulence of E. tarda in vivo Our work provides evidence that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, highlighting the importance of the intramacrophage infection cycle for the pathogenesis of E. tarda.

Dataset Information

Functional genomics approach to the identification of virulence genes involved in Edwardsiella tarda pathogenesis.

Publications

Functional genomics approach to the identification of virulence genes involved in Edwardsiella tarda pathogenesis.

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