Phylogenetic distribution of extraintestinal virulence-associated traits in Escherichia coli

The 72 member strains of the Escherichia coli Reference collection were ass essed as to genotype for 31 putative extraintestinal virulence factor (VF) genes and DNA sequence for papA, the P fimbrial structural subunit gene. Al though most VFs were concentrated in phylogenetic group B2 or jointly in gr oups B2 and D, others were concentrated primarily in group D, were broadly distributed (without group-specific associations), and/or occurred only out side of group B2. Statistical correlations among VFs suggested linkage on p athogenicity-associated islands or plasmids. Isolates from humans and nonhu man primates had more VFs than did isolates from other animals. Sequence di versity was minimal within each F type-specific papA allele group but was s ubstantial 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 extra intestinal VFs in E. coli.