Background The distinguishing characteristics of extraintestinal pathogenic Escherichia coli (ExPEC) strains are incompletely defined. Methods We characterized 292 diverse-source human Escherichia coli isolates (116 from fecal specimens, 79 from urine specimens [of which 39 were from patients with cystitis and 40 were from patients with pyelonephritis], and 97 from blood specimens) for phylogenetic group, sequence type complex (STc), and 49 putative extraintestinal pathogenic E. coli (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 the following bacterial traits as independent predictors of illness severity both overall and among the fecal and clinical (ie, urine and blood) 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 (ie, clinical vs fecal) nor molecular ExPEC status added predictive power to these traits, which accounted collectively for up to 49% of the observed variation in virulence. Conclusions Among human-source E. coli isolates, specific accessory traits and phylogenetic/clonal backgrounds predict experimental virulence in a murine sepsis model better than does ecological source.
Bibliographical noteFunding Information:
Financial support. This work was supported in by the Office of Research and Development, Department of Veterans Affairs (grants 1 I01 CX000920-01 and 2I01CX000920-04 to J. R. J.) and the National Institutes of Health (grant R21AI117654 to L. B. P.).
© Published by Oxford University Press for the Infectious Diseases Society of America 2018.
Copyright 2019 Elsevier B.V., All rights reserved.
- Escherichia coli
- clinical isolates
- fecal isolates
- mouse models
- phylogenetic groups
- sequence types
- virulence factors