Urine specimens have been considered to be sterile in the absence of a clinically identifiable infection. However, recent evidence suggests that the bladder harbours commensal bacteria different among men, pre- and post-menopausal healthy women [Ref.1,2]. Whether the bladder microbiota contributes to lower urinary tract symptoms (LUTS) remains known. The aim of this study is to determine how the bladder microbiota are different between men and women with or without overactive bladder (OAB).

Urine specimens were collected from postmenopausal women with OAB (n=20) and pre-(n=20) and post- (n=20) menopausal women without LUTS using a transurethral catheter to avoid bacterial contamination from external tissues. Midstream urine specimens were also collected from age (postmenopause) matched-men with (n=20) or without (n=20) OAB. The DNA was extracted from the urine pellet, and bacterial 16S rRNA gene sequencing was performed using Illumina MiSeq. The bladder microbiota at the phylum and genus levels with low relative abundances (< 0.1%) were filtered and the remaining top 50 different types were analysed using Mann Whitney U-test.

At the phylum level, there were no significant differences in the relative abundance of microbiota between the pre-and postmenopausal controls (Fig.1A and 1B). At the genus level, the relative abundance of Lactobacillus and Gardnerella was significantly decreased and that of Peptoniphilus, Anaerococcus, Escherichia and Corynebacterium was significantly increased in the postmenopausal controls compared with the premenopausal controls. Next, the significantly increased abundance of Firmicutes and the significantly decreased abundance of Proteobacteria were seen in the age-matched male controls compared with the postmenopausal controls at the phylum level (Fig.1B and 1C). The relative abundance of Peptoniphilus, Anaerobacillus, Trabulsiella and Escherichia was significantly decreased and that of Streptococcus, Staphylococcus and Corynebacterium was significantly increased in the age-matched male controls compared with the postmenopausal controls at the genus level. On the other hand, there were no significant differences in the relative abundance of bladder microbiota between the postmenopausal controls and OAB patients as well as between the age-matched male controls and OAB patients at the phylum (Fig.1B and Fig.2A, Fig.1C and 2B) and genus levels, respectively.

The age and sex differences in the bladder microbiota were clearly demonstrated in this study. The significant increases in Peptoniphilus, Anaerococcus and Escherichia and the significant decreases in Lactobacillus and Gardnerella were seen in the postmenopausal controls. In addition, the dominant bacteria in the bladder were Peptoniphilus, Anaerobacillus, Trabulsiella and Escherichia in in the postmenopausal women, and Streptococcus, Staphylococcus and Corynebacterium in the age-matched men.

The results of this study suggest that, while there is the significant age and sex differences in bladder microbiota, commensal bacteria in the bladder do not contribute to OAB.

Fouts DE et al, J Transl Med 100: 174, 2012
Thomas-White KJ et al, Am J Obstet Gynecol 55: e1-16, 2017

Continence 2S2 (2022) 100365
DOI: 10.1016/j.cont.2022.100365