Methenamine Hippuate on the Urobiome of Postmenopausal Women with Recurrent UTI

Objectives: Postmenopausal women with recurrent urinary tract infections (RUTI) are repeatedly exposed to antibiotics for treatment and prophylaxis; therefore, they are at risk for colonization by multi-drug resistant organisms. Methenamine Hippurate (MH), a non-antibiotic alternative, has shown promise for the prevention of RUTI; however, the effect of MH on the urobiome of postmenopausal women with RUTI is not known. This study aims to determine the longitudinal consequences of MH on the urobiome of postmenopausal women with RUTI. We hypothesize that resident bladder microbiota of women with RUTI will be altered by administration of MH

Methods: A longitudinal study of postmenopausal women with a history of RUTI was conducted with evaluation of the urobiome for a three-month period. Participants were asked to collect daily voided urine specimens using the Peezy Midstream device during the following weeklong “windows:” (A) prior to initiating treatment with MH, (B) one week after initiation of treatment, (C) two weeks prior to 3-month follow-up appointment, and (D) one week before the 3-month follow-up appointment. For patients unable to collect an appropriate specimen with the Peezy, a subsequent specimen was collected by clean catch. Expanded Quantitative Urine Culture (EQUC) was used to assess diversity and urobiome composition of catheterized urine, voided urine, and peri-urethral swabs, while 16S rRNA gene amplicon sequencing was used to determine taxonomic classification, beta diversity and differential abundant analysis of voided urine only.

Results: Ten postmenopausal women were enrolled. Three participants did not complete the study due to allergic reaction, improper handling of specimens, and COVID infection. Thus, only 7 participants were considered for full analysis. There were no UTIs for any participant during the study period. Participants had an improvement in symptom assessment based on the Urinary Distress Inventory, such as frequency of urination, leakage due to urgency, and abdominal pain domains (Table 1). EQUC and 16S amplicon sequencing-based taxonomic classification revealed predominance of Enterobacteriaceae, especially E. coli, but also members of many Gram-positive genera, including several emerging uropathogens (Figure 1). Assessed by EQUC, catheterized urine specimens were significantly less diverse than both voided urine and periurethral specimens. Following initiation of MH therapy, the alpha diversity of only catheterized urine specimens increased. Beta diversity using Bray-Curtis dissimilarity matrices revealed voided urine (urogenital) microbiomes of most participants differed significantly during at least one post-treatment week relative to the pre-treatment composition. Differential abundance analysis revealed that many significantly different taxa were not amongst the most abundant.

Conclusions: MH treatment did not eliminate uropathogens. Instead, it uniquely altered each participant’s urogenital microbiome. To understand the mechanism of action, researchers should look beyond the suspected uropathogens, and consider both the participant and rest of their urogenital microbiome.