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Comparison of Asymptomatic Bacteriuria Escherichia coli Isolates from Healthy Individuals versus Those from Hospital Patients Shows that Long-Term Bladder Colonization Selects for Attenuated Virulence Phenotypes

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Author

  • Ellaine Salvador
  • Florian Wagenlehner
  • Christian-Daniel Koehler
  • Alexander Mellmann
  • Joerg Hacker
  • Catharina Svanborg
  • Ulrich Dobrindt

Summary, in English

Asymptomatic bacteriuria (ABU) is a condition where bacteria stably colonize the urinary tract, in a manner closely resembling commensalism at other mucosa! sites. The patients carry >10(5) CFU/ml for extended periods of time and rarely develop symptoms. Contrasting the properties of ABU strains to those of uropathogenic isolates causing symptomatic infection is therefore highly relevant to understand mechanisms of bacterial adaptation. The prototype ABU strain Escherichia coli 83972 has a smaller genome than uropathogenic E. coli (UPEC) strains with deletions or point mutations in several virulence genes, suggesting that ABU strains undergo a programmed reductive evolution within human hosts. This study addressed if these observations can be generalized. Strains causing ABU in outpatients or hospitalized patients after catheterization or other invasive procedures were compared to commensal E. coli isolates from the intestinal flora of healthy individuals. Notably, clonal complex 73 (CC73) was a prominent phylogenetic lineage dominated by ABU isolates. ABU isolates from outpatients and hospitalized patients had a similar overall virulence gene repertoire, which distinguished them from many commensals, but typical UPEC virulence genes were less frequently attenuated in hospital strains than in outpatient strains or commensals. The decreased virulence potential of outpatient ABU isolates relative to that of ABU strains from hospitalized patients supports the hypothesis that loss of expression or decay of virulence genes facilitates long-term carriage and adaptation to host environments.

Publishing year

2012

Language

English

Pages

668-678

Publication/Series

Infection and Immunity

Volume

80

Issue

2

Document type

Journal article

Publisher

American Society for Microbiology

Topic

  • Microbiology in the medical area
  • Immunology in the medical area

Status

Published

ISBN/ISSN/Other

  • ISSN: 1098-5522