The role of microbiota in the etiology of dysplastic and oncological diseases of the cervix, vagina, and vulva: A review

The vaginal microbiome: A complex milieu affecting risk of human papillomavirus persistence and cervical cancer

BackgroundFifteen longitudinal studies have shown associations between bacterial vaginosis and high risk human papillomavirus (hrHPV) acquisition and/or persistence, and/or cervical dysplasia. However, few studies assessed the vaginal microbiota (VMB) comprehensively,...

Associations between the vaginal microbiome and Candida colonization in women of reproductive age

The aetiology of bacterial vaginosis (BV) is not well-understood, and prevalence appears to be higher among women living in sub-Saharan Africa. A recent conceptual model implicates three main bacteria (Gardnerella vaginalis; Atopobium vaginae; and Prevotella bivia), sexual activity, sialidase activity, and biofilm formation in the pathogenesis of BV. We describe the vaginal microbiota, presence of the putative sialidase A gene of G. vaginalis, and biofilm among 386 adolescent girls aged 17 and 18 years in a cross-sectional study in Mwanza, Tanzania around the time of expected sexual debut. Vaginal swabs were collected and tested by quantitative polymerase chain reaction (qPCR) for five Lactobacillus species, G. vaginalis, A. vaginae, P. bivia, the sialidase A gene of G. vaginalis, and by fluorescence in situ hybridisation (FISH) for evidence of G. vaginalis and A. vaginae biofilm. We conducted a risk factor analysis of G. vaginalis, A. vaginae and P. bivia, and explored the associations between biofilm, the presence of the sialidase A gene, and non-optimal vaginal microbiota (Nugent 4–7). L. crispatus and L. iners were detected in 69 and 82% of girls, respectively. The prevalence of L. crispatus was higher than previously reported in earlier studies among East and Southern African women. G. vaginalis, A. vaginae, P. bivia were independently associated with reported penile-vaginal sex. Samples with all three BV-associated bacteria made up the highest proportion of samples with Nugent-BV compared to samples with each bacterium alone or together in pairs. Of the 238 girls with G. vaginalis, 63% had the sialidase A gene detected, though there was no difference by reported sexual activity (p = 0.197). Of the 191 girls with results for sialidase A gene and FISH, there was strong evidence for an increased presence of sialidase A gene among those with evidence of a biofilm (p < 0.001). There was a strong association between biofilm and non-optimal microbiota (aOR67.00; 95% CI 26.72–190.53). These results support several of the steps outlined in the conceptual model, although the role of sexual activity is less clear. We recommend longitudinal studies to better understand changes in vaginal microbiota and biofilm formation around the time of sexual debut.

Background: Vaginal microbiota dysbiosis could lead to the vaginal health conditions. This imbalance in vaginal microbiota can be due to a number of factors including contraceptive methods. Objective: This study was carrried out to investigate the vaginal microbiota dysbiosis and associated vaginal health outcomes among women under contraception at Musasa health Center. Materials and Methods: This was a cross sectional study. 56 vaginal swab samples were collected from women enrolled in a family planning program, and transported to INES Ruhengeri clinical microbiology laboratory for vaginal microbial community analysis. The outcomes were evaluated by scheduled interviews. Chi square test was used to evaluate association of microbiota imbalances in the vagina and the vaginal health outcomes. Results: Lactobacilli (92.85%) was the most predominant microorganism observed in the vagina. Outcomes of the vaginal microbiota dysbiosis under different contraceptive regimes were observed. Vaginal microbial community imbalance in different family planning methods was statistically significant (x2 = 36.5, P = 0.049048) to be associated with vaginal health outcomes such as bacterial vaginosis, urinary tract infections, candidiasis and vaginitis. The association with contraceptives contraceptive methods and vaginal microbial community dysbiosis was statistically significant (x2 = 96.2403, P = 0.000491). The Implant for 5 years and Intrauterine device (IUD) were statistically significant (x2 = 28.533, P = 0.002681 and x2 = 27, P = 0.004595 respectively) to contribute to the vaginal microbiota balance. Conclusion: This study established that family planning methods could cause vaginal dysbiosis thereby exposing the vagina to adverse health outcomes and poor reproductive health. Women undergoing family planning should seek medical support if any sign of vaginal infection is observed.

Objective: The ideal vaginal environment is maintained by Lactobacillus species, which keep the vagina clean and free of infections, boost fertility and immunity. Age-related decline in estrogen affects Lactobacillus population, leading to dominance of nonoptimal species and increased diversity in vaginal microbiota. In this study, we compared the differences between the vaginal microbiota of pre- and postmenopausal women. We also examined the relationships between vaginal and gut microbiota, their relationships with sex hormones and equol-producing ability. Materials and Methods: This was a cross-sectional study of 35 premenopausal and 35 postmenopausal women (age range: 27-76 years). We compared parameters such as the composition of the gut and vaginal microbiota, vaginal pH, estradiol, follicular stimulating hormone, and urinary equol concentration. Results: In the vaginal microbiota of premenopausal women, Lactobacillus species constituted ∼71.98%, and nonoptimal species constituted ∼16.87%. They were 10.08% and 26.78%, respectively, in the vaginal microbiota of postmenopausal women. The proportion of Lactobacillus was significantly low, whereas microbial diversity and vaginal pH were significantly high (p < 0.0001) in postmenopausal women. The compositions of the vaginal microbiota were significantly different in pre- and postmenopausal women. However, such differences were not noticeable in the gut microbiota. Urinary equol production had no significant correlation with vaginal microbiota, although it had significant relationships with gut microbiota in postmenopausal women. In both groups, the proportions of vaginal Lactobacillus were inversely correlated with vaginal microbial diversity and vaginal pH. Conclusion: Postmenopausal women had significantly low Lactobacillus and high nonoptimal species in their vaginal flora, whereas such age-related differences were not identified in gut microbiota. Urinary equol concentration had significant correlation with gut microbiota in postmenopausal women only. This study was registered with the University Hospital Medical Information Network (UMIN) Clinical Trial Registry (Trial registration No.: UMIN000043944).

The vaginal microbiota impact of antibiotic and probiotic compounds and point-of-care testing for vaginal dysbiosis and sexually transmitted infections

BackgroundPostpartum women often experience stress urinary incontinence (SUI) and vaginal microbial dysbiosis, which seriously affect women’s physical and mental health. Understanding the relationship between SUI and vaginal microbiota composition may help to prevent vaginal diseases, but research on the potential association between these conditions is limited.ResultsThis study employed 16S rRNA gene sequencing to explore the association between SUI and vaginal dysbiosis. In terms of the vaginal microbiota, both species richness and evenness were significantly higher in the SUI group. Additionally, the results of NMDS and species composition indicated that there were differences in the composition of the vaginal microbiota between the two groups. Specifically, compared to postpartum women without SUI (Non-SUI), the relative abundance of bacteria associated with bacterial dysbiosis, such as Streptococcus, Prevotella, Dialister, and Veillonella, showed an increase, while the relative abundance of Lactobacillus decreased in SUI patients. Furthermore, the vaginal microbial co-occurrence network of SUI patients displayed higher connectivity, complexity, and clustering.ConclusionThe study highlights the role of Lactobacillus in maintaining vaginal microbial homeostasis. It found a correlation between SUI and vaginal microbiota, indicating an increased risk of vaginal dysbiosis. The findings could enhance our understanding of the relationship between SUI and vaginal dysbiosis in postpartum women, providing valuable insights for preventing bacterial vaginal diseases and improving women’s health.

The human microbiome exhibits intricate populations across the body, with the vaginal tract serving as an ecosystem characterized by the prevalence of the genus Lactobacillus. Disruptions in the vaginal microbiota, which are frequently linked to variables such as sexual activity, hormonal fluctuations, and excessive use of antibiotics, can result in vaginal dysbiosis and the development of diseases such as bacterial vaginosis (BV) and candidiasis. Lactobacillus species, owing to their capacity to create an acidic environment through the production of lactic acid, have a key function within this complex microbial community: they inhibit the growth of harmful microorganisms. This study aimed to investigate the genomic characteristics of L. rhamnosus LR6, a newly discovered strain isolated from the vaginal microbiota of 20 healthy women to assess its potential as a vaginal probiotic. We performed a comparative investigation of the genetic traits of L. rhamnosus using 45 publicly available genomes from various sources. We evaluated the genetic characteristics related to carbohydrate utilization, adhesion to host cells, and the presence of bacteriocin clusters. A comprehensive study was conducted by integrating in silico evaluations with experimental techniques to authenticate the physiological characteristics of strain LR6. We further used a rat model to assess the impact of L. rhamnosus LR6 administration on the changes in the gastrointestinal tract and the vaginal microbiome. The assessments revealed a significantly high inhibitory activity against pathogens, enhanced adherence to host cells, and high lactic acid production. Rat experiments revealed changes in both the fecal and vaginal microbiota; in treated rats, Firmicutes increased in both; Lactobacillaceae increased in the fecal samples; and Enterobacteriaceae decreased but Enterococcaceae, Streptococcaceae, and Morganellaceae increased in the vaginal samples. The study results provide evidence of the genetic characteristics and probiotic properties of LR6, and suggest that oral administration of L. rhamnosus LR6 can alter both gut and vaginal microbiome. Collectively, these findings establish L. rhamnosus LR6 as a highly promising candidate for improving vaginal health.

Preterm birth, the leading cause of death in children under 5 years, may be caused by inflammation triggered by ascending vaginal infection. About 2 million cervical cerclages are performed annually to prevent preterm birth. The procedure is thought to provide structural support and maintain the endocervical mucus plug as a barrier to ascending infection. Two types of suture material are used for cerclage: monofilament or multifilament braided. Braided sutures are most frequently used, although no evidence exists to favor them over monofilament sutures. We assessed birth outcomes in a retrospective cohort of 678 women receiving cervical cerclage in five UK university hospitals and showed that braided cerclage was associated with increased intrauterine death (15% versus 5%; P = 0.0001) and preterm birth (28% versus 17%; P = 0.0006) compared to monofilament suture. To understand the potential underlying mechanism, we performed a prospective, longitudinal study of the vaginal microbiome in women at risk of preterm birth because of short cervical length (≤25 mm) who received braided (n = 25) or monofilament (n = 24) cerclage under comparable circumstances. Braided suture induced a persistent shift toward vaginal microbiome dysbiosis characterized by reduced Lactobacillus spp. and enrichment of pathobionts. Vaginal dysbiosis was associated with inflammatory cytokine and interstitial collagenase excretion into cervicovaginal fluid and premature cervical remodeling. Monofilament suture had comparatively minimal impact upon the vaginal microbiome and its interactions with the host. These data provide in vivo evidence that a dynamic shift of the human vaginal microbiome toward dysbiosis correlates with preterm birth.

Increasing evidence indicates that the vaginal microbiota (VMB) is closely associated with the development and progression of cervical diseases. Alterations in microbial composition have been observed across different stages of human papillomavirus (HPV) infection, cervical intraepithelial neoplasia (CIN), and cervical cancer. In healthy individuals, the VMB is typically dominated by Lactobacillus species, which contribute to the maintenance of an acidic environment and local immune balance. In contrast, vaginal dysbiosis is characterized by a reduction in Lactobacillus and an increased abundance of anaerobic bacteria, accompanied by elevated pH, disruption of epithelial barriers, and persistent inflammatory responses. Clinical and sequencing studies have reported that enrichment of specific bacterial genera, including Sneathia and Fusobacterium, is more frequently detected in high-grade cervical lesions, suggesting a potential association with disease severity. These microbial shifts may facilitate persistent HPV infection and promote lesion progression through multiple biological pathways. In addition, emerging evidence suggests that modulation of the VMB, particularly through probiotic supplementation with Lactobacillus crispatus, may support HPV clearance and improve microbial stability in early disease stages. By integrating findings from recent studies, this review outlines the dynamic changes of key microbial taxa during cervical disease progression and discusses their potential clinical relevance. These observations provide a quantitative reference for future investigations and highlight the possible value of microbiome-based strategies in cervical disease risk assessment and management.

Objectives:Cervical cancer is caused by persistent infection with oncogenic, or “high-risk” types of human papillomaviruses, and is the most common malignancy in Kenyan women. A longitudinal study was initiated to investigate factors associated with persistent human papillomavirus detection among HIV-infected and HIV-uninfected Kenyan women without evidence of cervical dysplasia.Methods:Demographic/behavioral data and cervical swabs were collected from HIV-uninfected women (n = 82) and HIV-infected women (n = 101) at enrollment and annually for 2 years. Human papillomavirus typing was performed on swabs (Roche Linear Array). Logistic regression models of human papillomavirus persistence were adjusted for demographic and behavioral characteristics.Results:HIV-infected women were older and less likely to be married and to own a home and had more lifetime sexual partners than HIV-uninfected women. All HIV-infected women were receiving anti-retroviral therapy at enrollment and had satisfactory CD4 cell counts and HIV viral loads. One- and two-year persistent human papillomavirus detection was significantly associated with HIV infection for any human papillomavirus, high-risk human papillomavirus, International Agency for the Research on Cancer-classified high-risk human papillomavirus, and non-oncogenic “low-risk” human papillomavirus.Conclusion:Persistent detection of oncogenic and non-oncogenic human papillomavirus was strongly associated with HIV infection in Kenyan women with re-constituted immune systems based on satisfactory CD4 cell counts. In addition to HIV infection, factors associated with an increased risk of human papillomavirus persistence included a higher number of lifetime sex partners. Factors associated with decreased risk of human papillomavirus persistence included older age and being married. Further studies are needed to identify the immunological defects in HIV-infected women that allow human papillomavirus persistence, even in women receiving effective anti-retroviral therapy. Further studies are also needed to determine the significance of low-risk human papillomavirus persistence in HIV-infected women.

Study question In subfertile patients, do the endometrial and vaginal microbiome correspond to one another when applying high-throughput culturing techniques? Summary answer High interpatient variation was observed in the number of different isolated species. Furthermore, there was a diverse patient-specific concordance between vaginal and endometrial microbiota profiles. What is known already The microbiome of the female reproductive tract is potentially implicated in fertility and in vitro fertilization success rates. Of particular interest is Lactobacillus iners, an ineffective lactic acid producer, that is related with vaginal dysbiosis and adverse reproductive health outcomes. Previous metagenomics-based studies have highlighted that the endometrial and vaginal microbiome can be quite distinct in the same patient. Here, we investigated the applicability of a novel methodology, i.e. culturomics, in studying the vaginal-uterine microbiome. In contrast to metagenomics, a culturomics-generated microbiome profile is not influenced by depth bias or DNA contamination from extraction kits and reagents. Study design, size, duration In this pilot study, paired samples of vaginal swabs and endometrial biopsies were obtained from six subfertile women undergoing a diagnostic hysteroscopy. Vaginal swabs were taken prior to the hysteroscopy, while biopsies were harvested afterwards, with a pipelle technique. Participants/materials, setting, methods A plethora of enrichment broths and (non)selective agars were processed in an aerobic and anaerobic manner to ensure exhaustive culturomics results. Agars were incubated until 30 days post-inoculation and processed applying the Copan WASPLab® system. Bacterial colonies were identified using the Brüker MALDITOF MS Biotyper® system. Main results and the role of chance A total of 3218 colonies were detected using the MALDI Biotyper® system, enabling the identification of 79 different species. High inter-patient variability was observed in the number of detected isolated species (11–49). Also, the concordance between vaginal and endometrial microbiota differed from 4 to 48 %. Interestingly, the percentage of vagino-endometrial similarity and microbial diversity seemed to be associated with the presence of certain Lactobacillus species. We observed that the less diverse microbiome profiles (11-27 species) were dominated by eubiosis-related strains such as L. crispatus, L. jensenii, L. gasseri, L. salivarius and L. vaginalis, while the more diverse microbiome profile (49 species) was colonized by de dysbiosis-associated L. iners. Limitations, reasons for caution Only a small number of patients was included as this was a proof-of-principle study investigating the applicability of culturomics on vaginal swabs/endometrial biopsies. Wider implications of the findings Culturomics-acquired microbiome profiles could have a place in personalized fertility medicine with potential implications in therapy. The true value of our findings and their relationship with endometrial pathologies and IVF success rates needs to be confirmed in larger series. Trial registration number 143201420916

Study question Do rectal, vaginal, and seminal microbiomes influence chances of achieving pregnancy and subsequent pregnancy outcomes following Assisted Reproductive Technology (ART)? Summary answer A Lactobacillus-depleted vaginal microbiome was associated with lower pregnancy and live birth rates in ART, while specific bacterial taxa correlated with reproductive success or failure. What is known already The human microbiome plays a vital role in health and fertility. Vaginal dysbiosis has been linked to pregnancy loss and reduced success rates in assisted reproductive techniques. The gut microbiome has been associated with infertility-related conditions like endometriosis and Polycystic Ovary Syndrome. Finally, emerging evidence suggests that the seminal microbiota may influence semen quality and DNA fragmentation. While the vaginal microbiome is relatively well-studied, research on the gut and semen microbiomes in relation to fertility remains limited. Additionally, most vaginal microbiome studies rely on 16S rRNA sequencing, microscopy, or culturing, which may overlook important microbial diversity. Study design, size, duration This multicenter prospective cohort study investigated the impact of the microbiome on pregnancy likelihood and outcomes in couples undergoing ART. Herein, whole-genome sequencing was performed on vaginal and rectal microbiome samples from 251 menstrual cycles among 249 women, as well as semen microbiome samples from 97 men. Participants for this study were recruited while undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) between June 2022 and October 2023 at four different University hospitals. Participants/materials, setting, methods Participants completed detailed questionnaires on medical and fertility history. Vaginal and rectal samples were self-collected in either the late follicular or luteal phase and preserved in DNA/RNA Shield, while a raw semen sample was collected from the sample used for fertilization. Libraries were sequenced on an MGI T7 sequencer using paired-end 150-bp reads, achieving a depth of at least 30 million reads for vaginal and rectal samples and 45 million reads for semen samples. Main results and the role of chance Vaginal microbiome analysis showed that most women were Lactobacillus dominant (around 50% had high prevalence of Lactobacillus crispatus). Alpha diversity – observed, Shannon and Pielou evenness - was slightly higher in the group with a positive pregnancy test and live-birth as compared to the group with a negative pregnancy test. Age did not differ significantly between groups. The main confounder influencing these results were occurrence of Pelvic Surgery, BMI and the underlying reason for infertility. For beta diversity, we observed significant clustering for all measures when we added a classification of a favorable or unfavorable microbiome composition to the analysis (Unfavorable profile defined as a relative load of Lactobacillus &amp;lt;20%, relative load of Lactobacillus jensenii &amp;gt;35%, presence of Gardnerella vaginalis or Proteobacteria &amp;gt;28% of total bacterial load). We observed that the group that conceived had higher relative prevalence of Varibacul massiliense, Peptococcus niger, Bifidobacterium breve, Prevotela colorans and lower relative abundance of Sneathia vaginalis, Clostriadiales bacterium, Anaerocuccus tetradium. Regarding live birth rate, we observed a positive relative abundance of Snethia vaginalis, Prevotella amnii and a lower relative abundance of Sneathia sanguinegens, Levyella massiliensis. Data regarding rectal and semen microbiome are currently under analysis and will be presented at ESHRE 2025. Limitations, reasons for caution This study includes a heterogeneous cohort with only few exclusion criteria. While we have comprehensive information on all participants, it can be challenging to control for all confounders, which could influence the results. The prospective observational design of the study allows for investigation of associations but does not establish causality. Wider implications of the findings These findings highlight the potential role of the vaginal microbiome in ART outcomes, emphasizing the need for further research into microbial influences on fertility. Expanding investigations into the rectal and seminal microbiomes may provide a broader understanding of their impact on reproductive success, potentially leading to improved clinical strategies. Trial registration number Yes

Study question Can vaginal microbiota transplantation with shotgun-verified eubiotic vaginal microbiome over three menstrual cycles, convert vaginal dysbiosis to eubiosis in healthy women? Summary answer The RCT is ongoing until it is by March 2023. Results will be ready for presentation at EHSRE conference. What is known already Vaginal dysbiosis covers imbalances in the vaginal flora, caused by the composition of bacteria, viruses, and vaginal fungi. A large proportion of women who have vaginal dysbiosis do not experience any symptoms. Dysbiosis occurs in about 16-20% of all women. Vaginal dysbiosis is associated with infertility, euploid pregnancy loss, preterm labour or bacterial vaginosis. Treatment of vaginal dysbiosis consists of antibiotic treatment, and/or probiotics. Vaginal transplantation with eubiotic vaginal bacterial flora in combination with antibiotics has successfully been performed in four out of five recipients in an earlier study, but no study has been performed without use of antibiotic pretreatment. Study design, size, duration Randomized, controlled, double-blinded trial with a randomization ratio 3:1 to receive either a eubiotic microbiome transplant or placebo. 320 healthy women between 18 and 40 years, was enrolled for screening of vaginal dysbiosis. 30 donors with a eubiotic vaginal microbiome and 48 recipients with a dysbiotic microbiome were identified. The trial began in June 2021 and will end in March 2023 Participants/materials, setting, methods Vaginal microbiome composition was assed by next-generation ShotGun sequencing. To qualify as donor bacterial DNA from a vaginal swab had to show a bacterial composition of at least 80% lactobacilli and less than 5% pathogenic bacteria. To qualify as recipient vaginal microbiome composition should be with at least 20% pathogenic bacteria and no more than 10% lactobacilli. The recipient could have up to three attempts of VMT treatments with a follow-up period of 6 months. Main results and the role of chance We expect the RCT to end in March 2023, and the results of this trial will be presented at the ESHRE annual meeting . If we can show engraftment of a eubiotic microbiome transplant without the use of pre-treatment with antibiotics it could be a potential treatment of vaginal dysbiosis. Limitations, reasons for caution As this is the first VMT without antibiotic pretreatment we did not have reliable data for our power calculation and a negative result may be due to lack of statistical power. Wider implications of the findings Effective treatments for vaginal dysbiosis are urgently needed and VMT may be one such treatment strategy. Trial registration number NCT04855006