LAUSR

The phylogeny of the Escherichia coli species, with the identification of seven phylogroups (A, B1, B2, C, D, E and F), is linked to the lifestyle of the strains. With the accumulation of whole genome sequence data, it became clear that some strains belong to a group intermediate between the F and B2 phylogroups, designated as phylogroup G. Here, we studied the complete sequences of 112 strains representative of the G phylogroup diversity and showed that it is composed of one main sequence type complex (STc)117 and four other STcs (STc657, STc454, STc738 and STc174). STc117, which phylogeny is characterised by very short internal branches, exhibits extensive O diversity, but little H-type and fimH allele diversity while the other STcs are characterised by a main O, H and fimH type. STc117 strains possess many traits associated with extra-intestinal virulence, are virulent in a mouse sepsis model and exhibit multi-drug resistance such as CTX-M production. Epidemiologic data on 4524 Australian and French strains suggest that STc117 is a poultry associated lineage that can also establish in humans and cause extra-intestinal diseases. We propose an easy identification method that will help to trace this potentially virulent and resistant phylogroup in epidemiologic studies. This article is protected by copyright. All rights reserved.