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Asymptomatic bacterial colonization of the urinary bladder (asymptomatic bacteriuria, ABU) can prevent bladder colonization by uropathogens and thus symptomatic urinary tract infection (UTI). Deliberate bladder colonization with Escherichia coli ABU isolate 83972 has been shown to outcompete uropathogens and prevent symptomatic UTI by bacterial interference. Many ABU isolates evolved from uropathogenic ancestors and, although attenuated, may still be able to express virulence-associated factors. Our aim was to screen for efficient and safe candidate strains that could be used as alternatives to E. coli 83972 for preventive and therapeutic bladder colonization. To identify ABU E. coli strains with minimal virulence potential but maximal interference efficiency, we compared nine ABU isolates from diabetic patients regarding their virulence- and fitness-associated phenotypes in vitro, their virulence in a murine model of sepsis and their genome content. We identified strains in competitive growth experiments, which successfully interfere with colonization of ABU isolate 83972 or uropathogenic E. coli strain 536. Six isolates were able to outcompete E. coli 83972 and two of them also outcompeted UPEC 536 during growth in urine. Superior competitiveness was not simply a result of better growth abilities in urine, but seems also to involve expression of antagonistic factors. Competitiveness in urine did not correlate with the prevalence of determinants coding for adhesins, iron uptake, toxins, and antagonistic factors. Three ABU strains (isolates 61, 106, and 123) with superior competitiveness relative to ABU model strain 83972 display low in vivo virulence in a murine sepsis model, and susceptibility to antibiotics. They belong to different phylogroups and differ in the presence of ExPEC virulence- and fitness-associated genes. Importantly, they all lack marked cytotoxic activity and exhibit a high LD50 value in the sepsis model. These strains represent promising candidates for a more detailed assessment of relevant fitness traits in urine and their suitability for therapeutic bladder colonization. [ABSTRACT FROM AUTHOR]

It has been reported that urinary interleukin-6 (IL-6) and IL-8 levels are decreased in adult diabetic women with asymptomatic bacteriuria (ASB) when compared with non-diabetic women with ASB. Such impaired cytokine excretion might play a role in the higher prevalence of ASB among diabetic subjects. The aim of this study was to examine the urinary IL profile in children and young adults with type 1 diabetes mellitus (T1DM) with and without ASB. Midstream clean voiding urine samples were collected and cultured from 133 patients with T1DM (age: 15.6 ± 5.7 yr) and 178 controls (14.1 ± 4.7 yr) for two consecutive days. ASB was diagnosed in the case of ≥105 bacteria/mL. The urinary IL-6 and IL-8 concentrations were determined, and the presence of leukocyturia was also recorded. The prevalence of ASB was 16.5% in diabetic subjects and 2.8% in controls (p = 0.001). There was no difference between the diabetic and the control groups in the prevalence of ‘IL-6-uria’ (21.9 vs. 18.0%; p = 0.41), but IL-8 was more frequently detectable in the diabetic group (47.4 vs. 27.5%; p = 0.001). In individuals with ASB, the IL-8 level was similar in the diabetic (median: 70.0 pg/mg creatinine) and control group (42.3 pg/mg creatinine; p = 0.8). Indeed, the IL-8 levels were higher in diabetic subjects with ASB as compared with those without it (70.0 vs. <3.1 pg/mg creatinine; p = 0.001), and there was a significant association between the urinary IL-8 concentration and the bacterial count (p = 0.001). Diabetic patients with leukocyturia had higher IL-8 concentration than those without it (20.9 vs. <3.1 pg/mg creatinine; p = 0.003). Weak significant correlation was found between urinary IL-8 and hemoglobin A1c (HbA1c) (r = 0.4; p = 0.002). The sensitivity and specificity of leukocyturia were 50 and 89.9% in the whole population and those of IL-8 were 74.1 and 67.5%, respectively. In diabetic patients, 36.4% of the bacteriuria were gram-negative and 63.6% gram-positive. Our results suggest that diabetic children with ASB mount an IL-8 response to pathogens, which is comparable to non-diabetic children with bacteriuria. Thus, early in the natural history of diabetes, there are no significant changes in the IL response of children with ASB, as previously reported in adults. [ABSTRACT FROM AUTHOR]