Vaginal Microbiota
By Prof. Markku Voutilainen
Turku University Faculty of Medicine; Turku University Hospital, Department of Gastroenterology, Turku, Finland
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Created
24 August 2021
Updated
05 November 2021
VAGINAL DYSBIOSIS AND RECURRENT IMPLANTATION FAILURE
Recurrent implantation failure (RIF) is defined as a failure to achieve a clinical pregnancy after transfer of at least four good-quality embryos in a woman under the age of 40 years. Embryonal and uterine factors or maternal systemic diseases may cause RIF, but some women do not have recognizable etiology. The authors focused on the vaginal microbiota and metabolome of women with RIF. They found that RIF patients suffered vaginal dysbiosis, having a more diverse and abundant bacteria with an increase of many anaerobic and aerobic bacteria which could be linked to bacterial vaginosis and aerobic vaginitis or urinary tract infection, respectively. Conversely, at genus level their vaginal microbiota was decreased in Lactobacillus (LB); at species level L. iners was reduced and L. crispatus was the most abundant species in the RIF group. Increased vaginal bacterial diversity, LB depletion and related metabolic changes could serve as biomarkers capable of predicting the risk of RIF.
THE ROLE OF VAGINAL MICROBIOTA IN URINARY TRACT INFECTIONS
This review summarizes the role played by vaginal microbiota in urinary tract infections (UTI) as mounting evidence indicates that vagina may serve as a reservoir for uropathogens and increase susceptibility to UTI. Escherichia coli is the commonest cause of UTI and can colonize the vagina, which can be increased if the vaginal Lactobacillus (LB) colonization is reduced. Some vaginal bacteria are frequently detected in the urine but are underappreciated as uropathogens, because they are difficult to detect in routine clinical practice. For example, bacterial vaginosis (BV) is characterized by Gram-negative anaerobes, species belonging to Actinobacteria and Firmicutes phyla while LB is reduced and BV patients have a higher UTI risk. Gardnerella vaginalis is detected in BV and can cause acute or recurrent UTI. Group B Streptococcus may cause both aerobic vaginitis and UTI. Finally, some vaginal bacteria may enter the urinary tract and can transit briefly, cause immunomodulation or injury and unbalanced the host-pathogen interactions to influence the outcomes of uropathogenesis.
