title: 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.
abstract: Asymptomatic bacteriuria (ABU) is a condition where bacteria stably colonize the urinary tract, in a manner closely resembling commensalism at other mucosal 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.
authors: Institute for Molecular Biology of Infectious Diseases, University of Würzburg, Würzburg, Germany.
authors: Ellaine
authors: E
authors: Salvador
authors: Florian
authors: F
authors: Wagenlehner
authors: Christian-Daniel
authors: CD
authors: Köhler
authors: Alexander
authors: A
authors: Mellmann
authors: Jörg
authors: J
authors: Hacker
authors: Catharina
authors: C
authors: Svanborg
authors: Ulrich
authors: U
authors: Dobrindt
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001437:Bacteriuria / Q000382:microbiology*; D002648:Child; D016000:Cluster Analysis; D004926:Escherichia coli / Q000235:genetics* / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology*; D005260:Female; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006760:Hospitalization; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D012641:Selection, Genetic; D013997:Time Factors; D001743:Urinary Bladder / Q000382:microbiology*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins