Elevated urine IL-10 concentrations associate with persistence in older patients susceptible to recurrent urinary tract infections.

BACKGROUND

Age is a significant risk factor for recurrent urinary tract (rUTI) infections, but the clinical picture is often confused in older patients who also present with asymptomatic bacteriuria (ASB). Yet, how bacteriuria establishes in such patients and the factors underpinning and/or driving symptomatic UTI episodes are still not understood. To explore this further a pilot study was completed in which 30 male and female community based older patients (mean age 75y) presenting clinically with ASB / rUTIs and 15 control volunteers (72y) were recruited and monitored for up to 6 months. During this period symptomatic UTI episodes were recorded and urines collected for urinary cytokine and uropathogenic (UPEC) analyses.

RESULTS

Eighty-six per cent of patients carried (10 ≥ 10 CFU/ml urine) at some point throughout the study and molecular typing identified 26 different strains in total. Analyses of urine samples for ten different cytokines identified substantial patient variability. However, when examined longitudinally the pro-inflammatory markers, IL-1 and IL-8, and the anti-inflammatory markers, IL-5 and IL-10, were significantly different in the patient urines compared to those of the controls ( < 0.0001). Furthermore, analysing the cytokine data of the rUTI susceptible cohort in relation to carriage, showed the mean IL-10 concentration to be significantly elevated ( = 0.04), in patients displaying numbers ≥10 CFU/ml.

CONCLUSIONS

These pilot study data suggest that bacteriuria, characteristic of older rUTI patients, is associated with an immune homeostasis in the urinary tract involving the synthesis and activities of the pro and anti-inflammatory cytokines IL-1, IL-5, IL-8 and IL-10. Data also suggests a role for IL-10 in regulating bacterial persistence.