Phylogenetic distribution of extraintestinal virulence-associated traits in Escherichia coli

The 72 member strains of the Escherichia coli Reference collection were assessed as to genotype for 31 putative extraintestinal virulence factor (VF) genes and DNA sequence for papA, the P fimbrial structural subunit gene. Although most VFs were concentrated in phylogenetic group B2 or jointly in groups B2 and D, others were concentrated primarily in group D, were broadly distributed (without group-specific associations), and/or occurred only outside of group B2. Statistical correlations among VFs suggested linkage on pathogenicity-associated islands or plasmids. Isolates from humans and nonhuman primates had more VFs than did isolates from other animals. Sequence diversity was minimal within each F type-specific papA allele group but was substantial among different papA allele groups. The distribution patterns of papA variants and other VFs suggested multiple horizontal transfer events. These findings provide new insights into the phylogenetic origins of extraintestinal VFs in E. coli.