Gardnerella vaginalis in Recurrent Urinary Tract Infection Is Associated with Dysbiosis of the Bladder Microbiome

Abstract

Recent studies on the urine microbiome have highlighted the importance of the gut-vagina-bladder axis in recurrent urinary tract infection (rUTI). In particular, the role of <i>Gardnerella</i> as a covert pathogen that activates <i>E. coli</i> in animal experiments has been reported. Herein, we conducted a human bladder microbiome study to investigate the effect of <i>Gardnerella</i> on rUTI. Urine 16S ribosomal RNA gene sequencing via transurethral catheterization was conducted in the normal control group (NC) (<i>n</i> = 18) and rUTI group (<i>n</i> = 78). The positive detection rate of <i>Gardnerella</i> species did not differ between the NC and rUTI groups (22.2% vs. 18.0%, <i>p</i> = 0.677). In addition, the <i>Gardnerella</i>-positive NC and <i>Gardnerella</i>-positive rUTI groups showed similar levels of microbiome diversity. The <i>Gardnerella</i>-positive group was categorized into three subgroups: the <i>Escherichia</i>-dominant group, <i>Gardnerella</i>-dominant group, and <i>Lactobacillus</i>-dominant group. All of the <i>Escherichia</i>-dominant groups were associated with rUTI. The <i>Gardnerella</i>-dominant or <i>Lactobacillus</i>-dominant groups expressed rUTI with symptoms when risk factors such as the degree of <i>Gardnerella</i> proliferation or causative agents of bacterial vaginosis were present. The presence of <i>Gardnerella</i> in the urine is considered to be related to rUTI depending on other risk factors. New guideline recommendations regarding antibiotic selection based on a novel method to detect the cause of rUTI may be required to reduce antibiotic resistance.