title: Sequencing and functional annotation of avian pathogenic Escherichia coli serogroup O78 strains reveal the evolution of E. coli lineages pathogenic for poultry via distinct mechanisms.
abstract: Avian pathogenic Escherichia coli (APEC) causes respiratory and systemic disease in poultry. Sequencing of a multilocus sequence type 95 (ST95) serogroup O1 strain previously indicated that APEC resembles E. coli causing extraintestinal human diseases. We sequenced the genomes of two strains of another dominant APEC lineage (ST23 serogroup O78 strains χ7122 and IMT2125) and compared them to each other and to the reannotated APEC O1 sequence. For comparison, we also sequenced a human enterotoxigenic E. coli (ETEC) strain of the same ST23 serogroup O78 lineage. Phylogenetic analysis indicated that the APEC O78 strains were more closely related to human ST23 ETEC than to APEC O1, indicating that separation of pathotypes on the basis of their extraintestinal or diarrheagenic nature is not supported by their phylogeny. The accessory genome of APEC ST23 strains exhibited limited conservation of APEC O1 genomic islands and a distinct repertoire of virulence-associated loci. In light of this diversity, we surveyed the phenotype of 2,185 signature-tagged transposon mutants of χ7122 following intra-air sac inoculation of turkeys. This procedure identified novel APEC ST23 genes that play strain- and tissue-specific roles during infection. For example, genes mediating group 4 capsule synthesis were required for the virulence of χ7122 and were conserved in IMT2125 but absent from APEC O1. Our data reveal the genetic diversity of E. coli strains adapted to cause the same avian disease and indicate that the core genome of the ST23 lineage serves as a chassis for the evolution of E. coli strains adapted to cause avian or human disease via acquisition of distinct virulence genes.
authors.affiliation: Enteric Bacterial Pathogens Laboratory, Institute for Animal Health, Compton, Berkshire, United Kingdom.
authors.forename: Francis
authors.initials: F
authors.lastname: Dziva
authors.forename: Heidi
authors.initials: H
authors.lastname: Hauser
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Connor
authors.forename: Pauline M
authors.initials: PM
authors.lastname: van Diemen
authors.forename: Graham
authors.initials: G
authors.lastname: Prescott
authors.forename: Gemma C
authors.initials: GC
authors.lastname: Langridge
authors.forename: Sabine
authors.initials: S
authors.lastname: Eckert
authors.forename: Roy R
authors.initials: RR
authors.lastname: Chaudhuri
authors.forename: Christa
authors.initials: C
authors.lastname: Ewers
authors.forename: Melha
authors.initials: M
authors.lastname: Mellata
authors.forename: Suman
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: Roy
authors.initials: R
authors.lastname: Curtiss
authors.forename: Gordon
authors.initials: G
authors.lastname: Dougan
authors.forename: Lothar H
authors.initials: LH
authors.lastname: Wieler
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Thomson
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Pickard
authors.forename: Mark P
authors.initials: MP
authors.lastname: Stevens
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000145:classification* / Q000235:genetics* / Q000472:pathogenicity; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial / Q000235:genetics*; D007781:Lactoferrin / Q000172:deficiency; D007960:Leukocyte Disorders; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011201:Poultry Diseases / Q000382:microbiology*; D014422:Turkeys; D014774:Virulence
chemical_list: D004269:DNA, Bacterial; D036781:Fimbriae Proteins; D007781:Lactoferrin