Project name: Escherichia coli IMT2125

Description: Avian pathogenic Escherichia coli (APEC) comprise a diverse subgroup of extra-intestinalpathogenic E. coli (ExPEC) associated with respiratory and systemic disease in poultry.Recent studies have indicated that they may also pose a threat of zoonosis. Infections inpoultry are frequently due to serogroup O1, O2 and O78 strains, however APEC are highlyheterogenous and the mode and genetics of mucosal colonization and systemic translocationare ill-defined. We sequenced the genomes of sequence-type 23 APEC O78 strains chi7122(O78:H9) and IMT2125 (O78:H9) and compared them to each other and the re-annotated sequenceof APEC O1 (O1:K1:H7, sequence-type 95). This revealed that the O78 strains were far moreclosely related to each other than to APEC O1, with limited conservation of genomic islandsdescribed in APEC O1 and a distinct repertoire of virulence-associated loci. In light ofthe heterogeneity of APEC genomes, we surveyed the phenotype of 2185 random chi7122transposon mutants following intra-airsac inoculation of turkeys toward an understanding ofthe basis of virulence of APEC O78. The insertion site of 78 mutants that werenegatively-selected in the lung or liver relative to inocula was assigned bysignature-tagged mutagenesis. Phenotypes were supported by negative-selection of definednull mutants constructed by homologous recombination and novel genes and pathways that playstrain-specific and tissue-specific roles in infection were identified. For example, genesmediating group 4 (O-antigen) capsule synthesis were required for virulence of chi7122 andwere conserved in IMT2125 but absent from the sequenced serogroup O1 strain. Moreover,mutations in several genes were significantly attenuating at systemic sites, but not thelung. Such data will facilitate the development of cross-protective vaccines and otherstrategies to control a key endemic avian disease.

Data type: Genome sequencing and assembly

Sample scope: Monoisolate

Release date: 2012-08-02