The Role of the Bladder Microbiome in Lower Urinary Tract Disorders

Lower urinary tract symptoms (LUTS) cumulate a multitude of syndromes and urinary tract infections (UTI). This thesis focuses principally on recurrent UTIs (rUTIs) in renal transplant recipients and overactive bladder (OAB). In many cases, the cause of OAB is unknown. Recent studies in bladder microbial investigation have proposed that low-level bacteriuria or alterations in the bladder microbiome may be a cause for the symptoms of this syndrome. This thesis sets out to investigate the types of bacteria in the bladder of women with OAB and renal transplant recipients compared to asymptomatic controls by culturing urine samples and using 16s rRNA gene sequencing to identify exact species in each sample. The data is analysed alongside clinical data to determine better biomarkers for both rUTI and OAB. The results highlight that current hospital tests for infection are underreporting low-level infection and many of the biomarkers for infection do not correlate with incidence of infection. Here, the use of clue cells as a biomarker for rUTI is investigated for the first time with optimistic results. Furthermore, the alterations of the bladder microbiome over time post-renal transplant highlight consistently reduced incidence of particular species indicating shifts in the bladder microbiome in these patients. Using similar methods to explore the microbiome of women with OAB, it was found that there is a significant reduction of Lactobacillus, a crucial probiotic in the urogenitary tract that may be key to shifts in the bladder microbiome in OAB. The final section attempts to explore the physiology behind the symptoms of OAB in light of recent findings associating bacteria to OAB by looking at pericytes (a peri-vascular cell type found on capillaries). Pericytes are capable of transdifferentiating into myofibroblasts, a fibrotic cell which may increase spontaneous contraction in the bladder. This section investigates pericytes behaviour in the bladder in response to ATP, angiotensin, lipopolysaccharide and pro-inflammatory cytokines in a series of DIC imaging and immunohistochemistry experiments. The data supports this theory since pericytes constrict vessels upon acute stimulation and pericyte numbers dwindle with prolonged exposure. In conclusion, this thesis highlights the importance of correct testing for bladder infections and suggests that shifts in the bladder microbiome may be a cause for some lower urinary tract symptoms and this could be caused by pericyte responses to ATP and downstream cytokines

A case controlled study examining the bladder microbiome in women with Overactive Bladder (OAB) and healthy controls

Objective: To characterise the microbiome in healthy women with no bladder symptoms and to compare this to the bladder microbiome in patients with overactive bladder syndrome (OAB).Study design: MSU specimens from 63 women with OAB were compared to urine from 35 controls. Urine was centrifuged and the resulting sediment pellet was re-suspended in supernatant and plated under aerobic conditions for 48 h and anaerobic conditions for 7 days. Each morphologically distinct colony was purity plated. Bacterial colonies were lysed and polymerase chain reaction undertaken to amplify the 16 s ribosomal RNA gene. This DNA was purified and sequenced allowing identification of bacterial genera.Results: The mean number of different bacterial genera was 5.0 in both controls and OAB patients (p = 0.99). The uropathogenic bacteria Proteus (P = 0.01) was more commonly isolated from women with OAB. The genus lactobacillus was present less commonly in urine from OAB patients when compared to urine taken from controls (p = 0.02). Overall the most commonly grown bacteria were staphylococcus (grown in 59% of samples), streptococccus (51%), corynebacterium (37%) and lactobacillus (28%). A total of 95 different genera were identified from the urine samples.Conclusion: The female human bladder has a diverse microbiome with stastistically significant differences between bacterial species present in OAB patients and controls

Age, Menopausal Status and the Bladder Microbiome

Objectives: The bladder is not sterile but contains a healthy community of microbes termed the microbiome. Alterations in the bladder microbiome have been demonstrated in disease states such as the overactive bladder. The microbiome in other anatomical niches is known to alter with age eg the vagina. The objective of this study was to identify if the bladder microbiome in healthy women varies with age and menopausal status. Study design: Urine from 79 healthy women attending secondary care gynaecological clinics with no urinary symptoms provided clean catch mid-stream urine specimens. Urine was centrifuged and the resultant pellet was re-suspended and inoculated onto chocolate agar plates and cultured under either aerobic or anaerobic conditions. Morphologically different colonies were purity plated and 16s rRNA gene sequencing was performed. A microbe genomic basic local alignment search tool (BLAST) was used to identify the genus of the bacteria. Results: There was no significant correlation between the age of a woman and the number of different genera identified (r=-0.034, p=0.79). There were few significant differences in the frequency with which the majority of organisms were found in pre and post-menopausal women. The exceptions however were lactobacillus, which was more common in pre-menopausal women (31 vs 3 p=0.002) and Mobiluncus, which was more common in post-menopausal women (0 vs 3 p=0.02). Conclusions: There was no significant correlation between patient age and diversity of the bladder microbiome but large numbers of different organisms were identified. Significant differences were however observed for Lactobacillus which is more common in pre-menopausal women and Mobiluncus which is more common in in post-menopausal women

Altered urothelial ATP signaling in a major subset of human overactive bladder patients with pyuria

Overactive Bladder (OAB) is an idiopathic condition, characterized by urgency, urinary frequency, and urgency incontinence, in the absence of routinely traceable urinary infection. We have described microscopic pyuria (?10 wbc/?l) in patients suffering from the worst symptoms. It is established that inflammation is associated with increased ATP release from epithelial cells, and extracellular ATP originating from the urothelium following increased hydrostatic pressure is a mediator of bladder sensation. Here, using bladder biopsy samples, we have investigated urothelial ATP signaling in OAB patients with microscopic pyuria. Basal, but not stretch-evoked, release of ATP was significantly greater from the urothelium of OAB patients with pyuria than from non-OAB patients or OAB patients without pyuria (<10 wbc/?l). Basal ATP release from the urothelium of OAB patients with pyuria was inhibited by the P2 receptor antagonist suramin and abolished by the hemichannel blocker carbenoxolone, which differed from stretch-activated ATP release. Altered P2 receptor expression was evident in the urothelium from pyuric OAB patients. Furthermore, intracellular bacteria were visualized in shed urothelial cells from ?80% of OAB patients with pyuria. These data suggest that increased ATP release from the urothelium, involving bacterial colonization, may play a role in the heightened symptoms associated with pyuric OAB patients