The inference of a close genetic relationship between APEC and human ExPEC strains was further selleck chemicals substantiated by the distribution of tkt1. About 67% of UPEC and 76.4% of NMEC strains examined in this study harbor tkt1. Like many other virulence genes of ExPEC, tkt1 is also phylogenetically distributed. Of the ExPEC belonging to B2 phylogenetic group, 85.2% APEC, 94.0% of UPEC and 98.6% of NMEC were positive for tkt1. E. coli from phylogenetic group B2 have already

been experimentally and epidemiologically associated with extraintestinal infections [29, 30]. These results also suggest that tkt1 may play a role in the pathogenesis of human ExPEC as well as APEC. Genomic sequencing of APEC O1 revealed more than 40 genomic islands; several of them are theoretically involved in virulence [9]. Common features of most, if not all PAIs, include that they encode one or more virulence factors; range

in size from 10 to 200 kb; and are likely introduced into the genome via horizontal transfer, resulting in G-C ratios and codon usage that may deviate from the organism’s typical pattern. Often PAIs are flanked by small direct repeats and are associated with the 3′ end of tRNA genes. PAIS may be phage-derived, but some are thought to originate from plasmids. They may contain GW572016 mobility elements, such as integrons, transposons, and insertion AR-13324 research buy sequences, and if they move, are likely carried on plasmids, conjugative transposons, or phages, whose loss may spontaneously convert a virulent into an avirulent organism [6]. Similarly, the genomic island encoding tkt1 is 16 Kb in size and present in the APEC O1 genome but absent from the sequenced genome of the E. coli K12 strain MG1655. Moreover, the overall G+C content of this island is 48.57%, whereas the average G+C content of the E. coli K-12 genome is 50.8%. This discrepancy in G+C content further suggests that this particular

stretch of DNA does not belong to the E. coli K12 backbone and is foreign-derived. Also, the genomic island encoding tkt1 is localized in close proximity to tRNA genes. Unlike classical PAIs, no flanking direct repeats or mobility elements such as integrases or transposases were found in this genomic island. However, such mobility elements may have been lost during the evolutionary process. Horizontal transfer of genes 3-oxoacyl-(acyl-carrier-protein) reductase by genomic islands or PAIs is a common phenomenon in extracellular bacterial pathogens. The acquisition of genes in this way allows bacteria to adapt to a new or changing environment thus contributing to the fitness and/or virulence of the recipient organism. Table 2 ORFs present within the tkt1 genomic island ORF No. ORF name Location of ORF Function G+C content APECO1_2646   4312693..4312950 hypothetical protein NC_008563 APECO1_2645   4312947..4313438 hypothetical protein NC_008563 APECO1_2644   4313787..4314080 hypothetical protein NC_008563 APECO1_2643   4314532..4315122 putative sugar isomerase NC_008563 APECO1_2642   4315164..