Urinary Bacteria in Adult Women With Urgency Urinary Incontinence

Abstract

It was long believed that urine is sterile, when standard clinical microbiological culture techniques fail to detect bacteria. Recent evidence, however, has demonstrated that the bladder and urine of adult women contain bacteria not identified by standard culture. A number of studies using gene sequencing and culture have demonstrated that urine samples of some adult women found to be culture-negative using standard clinical microbiological techniques contain live bacteria, regardless of their urinary symptoms. The potential contribution of these previously unidentified uropathogens to the etiology of urinary urge incontinence (UUI) or other lower urinary tract disorders is unknown.

The aim of this study was to detect and quantify bacterial DNA in the baseline urine of participants enrolled in a randomized clinical trial who were about to undergo treatment for UUI without clinical evidence of urinary tract infection (UTI). Another study aim was to determine whether the presence of bacterial DNA in baseline urine is related to either baseline urinary symptoms or UTI risk after urinary tract instrumentation. All subjects (women without clinical evidence of baseline UTI) were randomized using a dual placebo approach to either a) cystoscopic onabotulinum toxin A injection plus an oral placebo or b) a cystoscopic placebo injection plus an oral anticholinergic. Bacterial DNA in catheter urine samples was measured using quantitative polymerase chain reaction (qPCR).

Urinary bacterial DNA was detected in 38.7% (60/155) of participants (qPCR-positive participants). Significantly more baseline daily episodes of UUI occurred in the 60 qPCR-positive participants than in the 95 qPCR-negative participants (mean [SD], 5.71 [2.60] vs 4.72 [2.86], P = 0.004). No association was found between symptom severity (assessed by questionnaire) or treatment outcome and either qPCR status or qPCR level in the qPCR-positive subjects. Ten percent (6/60) of the qPCR-positive women developed a UTI after treatment, compared with 24% (23/95) of the qPCR-negative women. There was no significant difference in the median qPCR level for samples greater than the detection limit among women who developed a UTI and those who did not (2.58 × 10⁵ vs 1.35 × 10⁵, P = 0.6).

These findings indicate that a unique population of urinary bacteria contributes to both baseline UUI and the risk for posttreatment UTI. The data, together with other emerging evidence, suggest that these bacteria could influence the diagnosis and treatment of UTI, UUI, and possibly other lower urinary tract disorders.