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.

Spectrum of Bacterial Colonization Associated with Urothelial Cells from Patients with Chronic Lower Urinary Tract Symptoms

“…Although the conventional wisdom holds that urine is sterile, the urethra connects the bladder to the outside environment, so it is not surprising that biological adaptation would enable commensal organisms to reside there. Indeed, reports of bacteriuria in normal controls are found in the literature (8,34,35). A reason why these commensal organisms are not readily detected may lie in the insensitivity of routine cultures, as shown here and by others previously (5)(6)(7)9).…”

Bacterial control of host gene expression through RNA polymerase II

“…Frequency of Pol II suppression among E. coli strains from APN, ABU, or the fecal flora We examined Pol II suppression in an epidemiologically defined collection of ABU isolates (n = 75) from which E. coli 83972 was derived (10,45,46). APN strains (n = 88) were obtained from children with febrile UTIs and fecal strains (n = 46) from children in the same area who had no history of UTI and negative urine cultures at screening.…”

Non-antibacterial alternative measures for urinary tract infection in children. Part 1. Suppression of the microbial initiation of the inflammation

“…В этой связи заслуживает внимания смена пара-дигмы в понимании так называемой бессимптомной бактериурии. Кишечные палочки при бессимптом-ной бактериурии ослабляют вирулентные феноти-пы, демонстрируя комменсальные взаимоотноше-ния по аналогии с похожими взаимоотношениями на других слизистых [19]. Этот защитный эффект бессимптомной бактериурии продемонстрирован у взрослых, когда в группе без ее лечения наблюда-лась в 4,5 раза меньшая частота обострений инфек-ции мочевой системы по сравнению с пациентами, получающими антибактериальную терапию.…”