Accessory Traits and Phylogenetic Background Predict Escherichia coli Extraintestinal Virulence Better than Does Ecological Source. Escherichia coli

Background: The distinguishing characteristics of extraintestinal pathogenicEscherichia coli (ExPEC) strains are incompletely defined.Methods: We characterized 292 diverse-source human E. coli isolates (116 fecal, 27cystitis, 30 pyelonephritis, 93 blood) for phylogenetic group, sequence type complex(STc), and 49 putative ExPEC-associated virulence genes. We then assessed thesetraits and ecological source as predictors of illness severity in a murine sepsis model.Results: The study isolates exhibited a broad range of virulence in mice. Most of thestudied bacterial characteristics corresponded significantly with experimental virulence,as did ecological source and established molecular definitions of ExPEC anduropathogenic E. coli (UPEC). Multivariable modeling identified similar bacterial traitsas independent predictors of illness severity both overall and among the fecal andclinical isolates separately: fyuA (yersiniabactin receptor), kpsM K1 (K1 capsule), andkpsM II (group 2 capsules). Molecular UPEC status predicted virulence independentlyonly among fecal isolates. Neither ecological source (e.g., clinical vs. fecal) normolecular ExPEC status added predictive power to these traits, which accountedcollectively for up to 49% of observed virulence variation.