In reproductive-age women, there is significant symptomatic overlap between interstitial cystitis/bladder pain syndrome, chronic pelvic pain, overactive bladder syndrome (OAB), vulvodynia, and endometriosis. The similarities in presenting symptoms often leads to misdiagnosis and delays in effective care. The epidemiology of pelvic pain suggests a microbial involvement in its etiology, but previous studies have failed to definitively identify specific bacteria associated with pain diagnoses. Given the substantial diagnostic confusion surrounding pelvic pain, we examined urinary bacterial associations with specific symptom clusters, not diagnoses, that we have previously identified and validated in multiple populations of subjects with the perception of bladder pain: bladder-specific pain symptoms (related to voiding cycle), non-urologic pelvic pain (perceived bladder pain unrelated to voiding cycle), and myofascial pelvic pain (pain attributable to the myofascial structure of the pelvic floor), which respond differently to therapeutic approaches to the managemnent of pelvic pain.

Catheterized urinary samples were obtained from 78 pre-menopausal women (age 18-45) with a variety of urinary complaints, including bladder and pelvic pain. 16S next-generation sequencing (NGS) was used to characterize urinary microbial populations; validated questionnaires (female Genitourinary Pain Index, OAB questionnaire, O’Leary-Sant Indices) were used to quantify symptom type and severity. K means unsupervised clustering analysis of NGS data was used to assign subjects to urotypes, based on the urinary bacterial community state types. Quantitative PCR (qPCR) served to confirm the NGS results and provide objective concentrations for taxa of interest. Linear regression analysis confirmed the associations of bacterial concentrations and specific symptoms/symptom clusters.

In a population of 78 reproductive-age women with perceived bladder pain who also expressed a variety of other urogenital complaints, 16S NGS revealed three urotypes that strongly correlated with symptomatology. Bladder-specific pain (worse with filling, relieved by voiding) was strongly associated with Lactobacillus iners, a Lactobacillus spp. that produces minimal lactic acid. Asymptomatic patients almost universally had a non-iners, Lactobacillus-predominant microbiota. Other urogenital pain, often vaginal and urethral pain unrelated to voiding, was positively correlated with increasing Enterobacteriaceae, confirmed on qPCR to be Escherichia coli. Detection of these two pathobiont species by qPCR in a second validation population (n=43) was highly predictive of each phenotype (P<0.00001). By qPCR, both pathobiont species were associated with increasing pain in a dose-dependent fashion. Patient with myofascial pelvic pain also had a non-iners Lactobacillus-dominant microbiota similar to controls.

We describe the identification of clinically-useful bacterial biomarkers for specific pelvic and bladder pain phenotypes. Objective, rapid, and inexpensive testing to identify and classify reproductive-age women with bladder and pelvic pain would allow more accurate diagnosis and improve treatment decisions. The direct association of pathobiont E. coli and L. iners concentrations with severity of specific pain symptoms implicates a microbial role in the pathogenesis of bladder-specific pain symptoms and non-urologic pelvic pain; however, subjects with myofascial pelvic pain were indistinguishable from controls, suggesting a different, non-bacteriologic etiology to this condition.

Microbial Biomarkers can distinguish different phenotypes of perceived bladder pain, which has the potential to help predict treatment responses as well as provide additional insight into the biological mechanisms of bladder pain.

Continence 12S (2024) 101587
DOI: 10.1016/j.cont.2024.101587