Ongoing horizontal and vertical transmission of virulence genes and papA alleles among Escherichia coli blood isolates from patients with diverse-source bacteremia

The phylogenetic distributions of multiple putative virulence factors (VFs) and papA (P fimbrial structural subunit) alleles among 182 Escherichia col i blood isolates from patients with diverse-source bacteremia were defined. Phylogenetic correspondence among these strains, the E. coli Reference (EC OR) collection, and other collections of extraintestinal pathogenic E. coli (ExPEC) was assessed. Although among the 182 bacteremia isolates phylogene tic group B2 predominated, exhibited the greatest concentration of individu al VFs, and contained the largest number of familiar virulent clones, other phylogenetic groups exhibited greater concentrations of certain VFs than d id group B2 and included several additional virulent clones. Certain of the newly detected VF genes, e.g., fyuA (yersiniabactin; 76%) and focG (F1C fi mbriae; 25%), were as prevalent or more prevalent than their more familiar traditional counterparts, e.g., iut (aerobactin; 57%) and sfaS (S fimbriae; 14%), thus possibly offering additional useful targets for preventive inte rventions. Considerable diversity of VF profiles was observed at every leve l within the phylogenetic tree, including even within individual lineages. This suggested that many different pathways can lead to extraintestinal vir ulence in E. coli and that the evolution of ExPEC, which involves extensive horizontal transmission of VFs and continuous remodeling of pathogenicity- associated islands, is a highly active, ongoing process.