Interpretation
Since the detection of microorganisms in the bladder of female without UTI,12 additional confirmatory evidence has clearly demonstrated the presence of a living bacterial community in the bladder of both women with and without lower urinary tract symptoms.2, 8, 13-15 This significant paradigm shift raises many questions about the role of the female urinary microflora in lower urinary tract health and disease. In this cross-section study, we characterized the differences of urinary microbiomes between the women with different degrees of OAB symptoms using high throughput sequencing of the bacterial 16S rRNA gene.
Besides diverse, the most common urotype in both groups wasLactobacillus , and similar results were observed by PRICE in UUI patients.16 In addition, we found mild group had a larger proportion of individuals with Lactobacillus -dominant urine, previous studies found that the UUI cohort exhibited decreasedLactobacillus sequence abundances compared to those for the control cohort,2 and in the 5mg Antimuscarinic responder group,Lactobacilluswas the most frequently cultivable urotype,17 in contrast, women who developed a post-treatment UTI had fewerLactobacillus sequences.6 Lactobacillusis best known for its dominance in vaginal microbiota and it can prevent vaginitis by maintaining a physiological acidic environment in the vagina. It seems pretty clear thatLactobacillusin the bladder also plays an important regulatory or protective role in functional lower urinary tract (LUT) disorders.
The bacterial diversity (number of unique bacterial species) and richness were increased in the moderate/severe patients urinary microbiome, in contrast, the evenness, represents the distribution of microbial species within the sample, was not statistically different. Although the M group has a smaller sample size than the M/S group, we further found statistically significant trends in terms of species diversity and richness by socres of OABSS, and confirmed that the higher the socres the higher the Observed species, Chao1, ACE, and Shannon’s index, verifying that the more severe the symptoms of OAB patients, the higher the diversity and richness of urine bacteria. This result is in consistent with the finding of PRICE16, but is inconsistent with the findings of Karstens L.5 PRICE et al. used an enhanced culture method called Expanded Quantitative Urine Culture (EQUC) coupled to MALDI-TOF mass spectrometry to identify the Chao1, ACE, and Shannon’s Indices were positively correlated to Urinary Distress Inventory (UDI) subscale score, which measures the severity of the disease.16But Karstens et al. found that lower microbial diversity was associated with increased symptom severity in women with UUI.5 We think this can be explained by the fact that two seemingly opposite structural changes in the bacterial flora are both destructive to the normal bacterial flora. Although little is known about the optimal characteristics of the urinary microbiome, extreme diversity is unlikely to be a preferred or advantageous biological state. The lowest diversity may be associated with a lack of beneficial microbes. At the other extreme, the increase in diversity may reflect the loss of the urinary flora regulation mechanism, which does not allow a healthy microbial community. Despite the differences in the composition of the inter-individual microbiota, individuals in the same group still have similarities in the urinary microbiota. as shown in the PCoA analysis that clustered mild group and moderate/severe group separately (Figure 2), indicating the possibility of a common urinary microbiota disorder associated with the same degree of OAB.
At phylum level, we detected thatActinobacteriaincreased significantly in the urine of moderate/severe patients, and our previous research found that compared with asymptomatic patients, OAB patients have significantly more Actinobacteria in their urine.8 These findings raise the possibility that dysbiotic microbial populations may play a role in the pathogenesis of OAB. At genus level, correlation analysis found that several specific bacteria are associated with different OAB sub-symptoms, some of which have also been reported by other researchers to be associated with LUTS. There was a positive correlation between abundance ofPrevotella and the degree of Nighttime frequency. Coincidentally, in Pearce et al.’s study,2 they found that enrichment of Prevotella was observed in UUI patients. Emerging studies have linked the increased abundance of Prevotella species to localized disease, including periodontitis, bacterial vaginosis, rheumatoid arthritis, metabolic disorders and low-grade inflammation.18 Apostolidis A et al. found bladder biopsies in patients with OAB revealed signs of chronic inflammation.19 This suggests that the bladder microbiome may participate in the occurrence and development of LUTS by causing chronic inflammation. We also detected that the more severe the symptoms of Nighttime frequency, the higher abundance ofPorphyromona . In addition, the same trend ofPorphyromona abundance changes was observed in Shoskes et al.’study, which revealed that chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) patients had over-representation of genusPorphyromona .20All these indicate that the intriguing possibility that specific microbial patterns may be linked to specific symptoms, which provides a great enlightenment for future researches of the urinary microbiome and the algorithms for the diagnosis and treatment of LUTS..