Urine and Tissue Bacterial Loads Correlate With Voiding Behaviors in a Murine Urinary Tract Infection Model

Abstract

Objectives: To describe associations between voiding behavior and bacterial loads in a murine model of urinary tract infection (UTI).

Methods: Fourteen female C57BL/6J mice were transurethrally inoculated with 10⁸colony-forming unit uropathogenic E. coli (UPEC) UTI89 in 50 μL two times, 24 hours apart. Voiding spot assays were used to measure voiding behavior. Voiding spot assays and urine cultures were performed at various time points between 1 and 28 days postinfection (dpi). Bladder and kidney bacterial loads were measured at 28 dpi. Correlations were calculated between voiding spot assay variables and bacterial loads at different dpi. In a separate experiment, 3 female mice were infected with UPEC in the same manner for histology changes at 28-dpi in chronic UTI.

Results: During the 28 days, among 14 mice, 8 developed chronic cystitis and 11 developed chronic pyelonephritis based on a priori definitions. All infected mice showed increased urinary frequency, polyuria, and decreased bladder capacity. Tissue fibrosis was also observed in the infected bladder. At 1 dpi and 28 dpi, the urinary bacterial loads were positively associated with frequency and polyuria. Bladder and kidney bacterial loads at 28 dpi were positively with frequency and polyuria.

Conclusions: Urine and tissue bacterial loads were associated with changes of voiding behavior at both 1 and 28 dpi.