The Female Microbiome in Patients Undergoing Bladder Instillation Therapy

The underlying pathophysiology for BPS/IC is currently an active area of research. There is speculation that there may be alteration in the bladder and vaginal microbiome that contributes to the symptomatology of BPS/IC, however existing literature is limited and contradictory. Nickel et al (2015) studied the bladder microbiota in women with IC/BPS during a flare versus nonflare. The study collected initial stream and midstream urine specimens and detected overall, there was no significant differences in the species composition. However, a greater prevalence of fungi (Candida and Saccharomyces) was seen in the flare group (15.7%) versus the non-flare group (3.9%) midstream urine specimens. Pearce et al (2015) sought to characterize the urinary microbiome via catheterized specimens from women with urgency urinary incontinence, a condition that can present similarly as IC/BPS. The study found that more than half of the patients were sequence positive, most commonly for Lactobacillus (45%) or Gardnerella (17%), with 25% made up of various other bacteria. In contrast, Abernethy et al (2017) showed via catheterized urine specimens from patients with IC/BPS that the urinary microbiome is less diverse and less likely to contain Lactobacillus species. There have been two recent studies investigating the female urinary microbiome in patients with IC/BPS. Nickel et al (2019) found no differences in species composition between urine from patients with IC/BPS versus controls. Meriwether et al (2019) reported similar findings, and additionally found no differences when comparing the vaginal bacterial microbiome in patients with IC/BPS versus controls. However, in evaluating the bladder microbiome, both studies utilized uncatheterized urine specimens. Wolfe et al (2012) showed microbiome differences between clean-catch and catheterized urine specimens, therefore vaginal contamination in both studies cannot be ruled out.