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Study: New link between vagina and bladder microbiota

Uropathogens may not be the only bacteria shared between the vagina and bladder.

Analysis of bacteria found in the urinary tract and vagina suggest that female urogenital microbiota are linked and might now be considered a “single urogenital microbiota,” according to research published in Nature Communications.Furthermore, the authors were able to show for the first time that the bacteria shared between the two sites are not limited to just uropathogens, but also consist of similar health-promoting Lactobacillusstrains, which may protect against urinary tract infections (UTI) as well as vaginal infections. 

The researchers obtained urine samples via transurethral catheterization of 77 perimenopausal women who were symptomatic and asymptomatic for UTI and compared them to publicly available gut (N=120) and vaginal (N=67) microbiota samples. 

Using an expanded quantitative urine culture (EQUC) technique they developed that can capture a broad range of bacterial taxa, the group collected 149 isolates characterizing 36 genera and 78 species. This collection represents approximately three-quarters of the genera within the bladder microbiota and is a valuable resource for exploring the functions of pathogenic and commensal bacteria in the bladder, the authors reported. They identified several harmful bacteria known to cause UTIs, including Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter cloaceae, Morganella morganii, and Pseudomonas aeruginosa, in the collectionHowever, these species represent only 7.7% (6/78) of known uropathogenic species in the bladder. Few Proteobacteria or Gram-negative bacteria were found. More abundant were Gram-positive phyla Firmicutes (47.4%), Actinobacteria (38.5%), Streptococcaceae (11.0%), Lactobacillceae (11.0%), Corynebacteriaceae (10.3%), and Actinomycetaceae (10.3%). 

They then compared the contents of the bladder microbiota from their genome culture collection to that found in the vagina and gastrointestinal (GI) tracts of unrelated healthy women. The only species detected at all three sites was Bifidobacterium bifidum. Twenty-three species were found in both the bladder and vagina; four of these species (Actinomyces neuii, Lactobacillus crispatus, L. gasseri, and L. jensenii) were highly similar in composition. Seven species that are often linked to UTIs were found in the urinary tracts of symptomatic women: E. cloacae, E. coli, P. aeruginosa, Bacillus infantis, K. pneumoniae, Gardnerella terraeand Bacillus idriensis. Genome sequencing and protein-coding analysis showed that the strains had similar functions in the bladder and vagina, but different functions in the GI tract. 

Lastly, the group compared bacterial strains found in the vagina and bladders of four women who had symptoms of urge urinary incontinence but no clinically detectable UTIs. The women were found to have S. anginsosus, E.coli, L. iners, and L. crispatus at both sites, and analysis of the strains revealed they were similar in composition to one another. “The existence of these closely related isolates provides strong evidence that bacterial movement between the vaginal and bladder microbiota is not only limited to ascending uropathogen species, such as E. coli…but also includes health-associated commensal bacteria,” the authors wrote. The group also suggested that Lactobacillusspecies may offer protection against UTIs just as they help to promote vaginal health.


By redefining the vaginal and urinary microbiota as one joint urogenital microbiota, new avenues may now be available for research and development of diagnostic tools and treatments for UTIs, urgency urinary incontinence, and other urinary tract disorders, the authors concluded.