Background: The distinguishing characteristics of extraintestinal pathogenic
Escherichia coli (ExPEC) strains are incompletely defined.
Methods: We characterized 292 diverse-source human E. coli isolates (116 fecal, 27
cystitis, 30 pyelonephritis, 93 blood) for phylogenetic group, sequence type complex
(STc), and 49 putative ExPEC-associated virulence genes. We then assessed these
traits 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 the
studied bacterial characteristics corresponded significantly with experimental virulence,
as did ecological source and established molecular definitions of ExPEC and
uropathogenic E. coli (UPEC). Multivariable modeling identified similar bacterial traits
as independent predictors of illness severity both overall and among the fecal and
clinical isolates separately: fyuA (yersiniabactin receptor), kpsM K1 (K1 capsule), and
kpsM II (group 2 capsules). Molecular UPEC status predicted virulence independently
only among fecal isolates. Neither ecological source (e.g., clinical vs. fecal) nor
molecular ExPEC status added predictive power to these traits, which accounted
collectively for up to 49% of observed virulence variation. Less...