Virulence properties of asymptomatic bacteriuria Escherichia coli

Int J Med Microbiol. 2009 Jan;299(1):53-63. doi: 10.1016/j.ijmm.2008.06.003. Epub 2008 Aug 15.


In asymptomatic bacteriuria (ABU), bacteria colonize the urinary tract without provoking symptoms. Here, we compared the virulence properties of a collection of ABU Escherichia coli strains to cystitis and pyelonephritis strains. Specific urinary tract infection (UTI)-associated virulence genes, hemagglutination characteristics, siderophore production, hemolysis, biofilm formation, and the ability of strains to adhere to and induce cytokine responses in epithelial cells were analyzed. ABU strains were phylogenetically related to strains that cause symptomatic UTI. However, the virulence properties of the ABU strains were variable and dependent on a combination of genotypic and phenotypic factors. Most ABU strains adhered poorly to epithelial cells; however, we also identified a subgroup of strongly adherent strains that were unable to stimulate an epithelial cell IL-6 cytokine response. Poor immune activation may represent one mechanism whereby ABU E. coli evade immune detection after the establishment of bacteriuria.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Bacterial Adhesion
  • Bacteriuria / microbiology*
  • Biofilms / growth & development
  • Cystitis / microbiology
  • Cytokines / metabolism
  • Epithelial Cells / microbiology
  • Escherichia coli / isolation & purification
  • Escherichia coli / pathogenicity*
  • Escherichia coli Infections / microbiology*
  • Escherichia coli Proteins / biosynthesis
  • Escherichia coli Proteins / genetics
  • Female
  • Hemagglutination
  • Hemolysis
  • Humans
  • Male
  • Middle Aged
  • Pyelonephritis / microbiology
  • Siderophores / biosynthesis
  • Urinary Tract Infections / microbiology*
  • Virulence Factors / biosynthesis*
  • Virulence Factors / genetics


  • Cytokines
  • Escherichia coli Proteins
  • Siderophores
  • Virulence Factors