title: tkt1, located on a novel pathogenicity island, is prevalent in avian and human extraintestinal pathogenic Escherichia coli.
abstract: BACKGROUND
  Extraintestinal pathogenic Escherichia coli are important pathogens of human and animal hosts. Some human and avian extraintestinal pathogenic E. coli are indistinguishable on the basis of diseases caused, multilocus sequence and phylogenetic typing, carriage of large virulence plasmids and traits known to be associated with extraintestinal pathogenic E. coli virulence.
  
  
  RESULTS
  The gene tkt1 identified by a previous signature-tagged transposon mutagenesis study, was found on a 16-kb genomic island of avian pathogenic Escherichia coli (APEC) O1, the first pathogenic Escherichia coli strain whose genome has been completely sequenced. tkt1 was present in 39.6% (38/96) of pathogenic Escherichia coli strains, while only 6.25% (3/48) of E. coli from the feces of apparently healthy chickens was positive. Further, tkt1 was predominantly present in extraintestinal pathogenic E. coli belonging to the B2 phylogenetic group, as compared to extraintestinal pathogenic E. coli of other phylogenetic groups. The tkt1-containing genomic island is inserted between the metE and ysgA genes of the E. coli K12 genome. Among different extraintestinal pathogenic E. coli of the B2 phylogenetic group, 61.7% of pathogenic Escherichia coli, 80.6% of human uropathogenic E.coli and 94.1% of human neonatal meningitis-causing E. coli, respectively, harbor a complete copy of this island; whereas, only a few avian fecal E. coli strains contained the complete island. Functional analysis showed that Tkt1 confers very little transketolase activity but is involved in peptide nitrogen metabolism.
  
  
  CONCLUSIONS
  These results suggest tkt1 and its corresponding genomic island are frequently associated with avian and human ExPEC and are involved in bipeptide metabolism.
authors.affiliation: Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary medicine, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Ganwu
authors.initials: G
authors.lastname: Li
authors.forename: Subhashinie
authors.initials: S
authors.lastname: Kariyawasam
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Tivendale
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Wannemuehler
authors.forename: Christa
authors.initials: C
authors.lastname: Ewers
authors.forename: Lothar H
authors.initials: LH
authors.lastname: Wieler
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Logue
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Nolan
mesh_terms: D000818:Animals; D015373:Bacterial Typing Techniques; D002645:Chickens / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics*; D044404:Genomic Islands; D006801:Humans; D058885:Multilocus Sequence Typing; D010455:Peptides / Q000378:metabolism; D010802:Phylogeny; D010957:Plasmids; D017422:Sequence Analysis, DNA; D014174:Transketolase / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D010455:Peptides; D014174:Transketolase