We conducted a systematic review of the Medline database (U.S. National Library of Medicine, National Institutes of Health, Bethesda, MD, U.S.A) to determine if consistent molecular vaginal microbiota (VMB) composition patterns can be discerned after a decade of molecular testing, and to evaluate demographic, behavioral and clinical determinants of VMB compositions. Studies were eligible when published between 1 January 2008 and 15 November 2013, and if at least one molecular technique (sequencing, PCR, DNA fingerprinting, or DNA hybridization) was used to characterize the VMB. Sixty three eligible studies were identified. These studies have now conclusively shown that lactobacilli-dominated VMB are associated with a healthy vaginal micro-environment and that bacterial vaginosis (BV) is best described as a polybacterial dysbiosis. The extent of dysbiosis correlates well with Nugent score and vaginal pH but not with the other Amsel criteria. Lactobacillus crispatus is more beneficial than L. iners. Longitudinal studies have shown that a L. crispatus-dominated VMB is more likely to shift to a L. iners-dominated or mixed lactobacilli VMB than to full dysbiosis. Data on VMB determinants are scarce and inconsistent, but dysbiosis is consistently associated with HIV, human papillomavirus (HPV), and Trichomonas vaginalis infection. In contrast, vaginal colonization with Candida spp. is more common in women with a lactobacilli-dominated VMB than in women with dysbiosis. Cervicovaginal mucosal immune responses to molecular VMB compositions have not yet been properly characterized. Molecular techniques have now become more affordable, and we make a case for incorporating them into larger epidemiological studies to address knowledge gaps in etiology and pathogenesis of dysbiosis, associations of different dysbiotic states with clinical outcomes, and to evaluate interventions aimed at restoring and maintaining a lactobacilli-dominated VMB.

BackgroundDespite their antimicrobial potential, vaginal lactobacilli often fail to retain dominance, resulting in overgrowth of the vagina by other bacteria, as observed with bacterial vaginosis. It remains elusive however to what extent interindividual differences in vaginal Lactobacillus community composition determine the stability of this microflora. In a prospective cohort of pregnant women we studied the stability of the normal vaginal microflora (assessed on Gram stain) as a function of the presence of the vaginal Lactobacillus index species (determined through culture and molecular analysis with tRFLP).ResultsFrom 100 consecutive Caucasian women vaginal swabs were obtained at mean gestational ages of 8.6 (SD 1.4), 21.2 (SD 1.3), and 32.4 (SD 1.7) weeks, respectively. Based on Gram stain, 77 women had normal or Lactobacillus-dominated vaginal microflora (VMF) during the first trimester, of which 18 had grade Ia (L. crispatus cell morphotypes) VMF (23.4%), 16 grade Iab (L. crispatus and other Lactobacillus cell morphotypes) VMF (20.8%), and 43 grade Ib (non-L. crispatus cell morphotypes) VMF (55.8%). Thirteen women with normal VMF at baseline, converted in the second or third trimester (16.9%) to abnormal VMF defined as VMF dominated by non-Lactobacillus bacteria. Compared to grade Ia and grade Iab VMF, grade Ib VMF were 10 times (RR = 9.49, 95% CI 1.30 – 69.40) more likely to convert from normal to abnormal VMF (p = 0.009). This was explained by the observation that normal VMF comprising L. gasseri/iners incurred a ten-fold increased risk of conversion to abnormal VMF relative to non-L. gasseri/iners VMF (RR 10.41, 95% CI 1.39–78.12, p = 0.008), whereas normal VMF comprising L. crispatus had a five-fold decreased risk of conversion to abnormal VMF relative to non-L. crispatus VMF (RR 0.20, 95% CI 0.05–0.89, p = 0.04).ConclusionThe presence of different Lactobacillus species with the normal vaginal microflora is a major determinant to the stability of this microflora in pregnancy: L. crispatus promotes the stability of the normal vaginal microflora while L. gasseri and/or L. iners predispose to some extent to the occurrence of abnormal vaginal microflora.

Cervicovaginal microbiota not dominated by lactobacilli may facilitate transmission of HIV and other sexually transmitted infections (STIs), as well as miscarriages, preterm births and sepsis in pregnant women. However, little is known about the exact nature of the microbiological changes that cause these adverse outcomes. In this study, cervical samples of 174 Rwandan female sex workers were analyzed cross-sectionally using a phylogenetic microarray. Furthermore, HIV-1 RNA concentrations were measured in cervicovaginal lavages of 58 HIV-positive women among them. We identified six microbiome clusters, representing a gradient from low semi-quantitative abundance and diversity dominated by Lactobacillus crispatus (cluster R-I, with R denoting 'Rwanda') and L. iners (R-II) to intermediate (R-V) and high abundance and diversity (R-III, R-IV and R-VI) dominated by a mixture of anaerobes, including Gardnerella, Atopobium and Prevotella species. Women in cluster R-I were less likely to have HIV (P ¼ 0.03), herpes simplex virus type 2 (HSV-2; Po0.01), and high-risk human papillomavirus (HPV; Po0.01) and had no bacterial STIs (P ¼ 0.15). Statistically significant trends in prevalence of viral STIs were found from low prevalence in cluster R-I, to higher prevalence in clusters R-II and R-V, and highest prevalence in clusters R-III/R-IV/R-VI. Furthermore, only 10% of HIV-positive women in clusters R-I/R-II, compared with 40% in cluster R-V, and 42% in clusters R-III/ R-IV/R-VI had detectable cervicovaginal HIV-1 RNA (P trend ¼ 0.03). We conclude that L. crispatusdominated, and to a lesser extent L. iners-dominated, cervicovaginal microbiota are associated with a lower prevalence of HIV/STIs and a lower likelihood of genital HIV-1 RNA shedding.

Background. It is widely assumed that the uterine cavity in non-pregnant women is physiologically sterile, also as a premise to the long-held view that human infants develop in a sterile uterine environment, though likely reflecting under-appraisal of the extent of the human bacterial metacommunity. In an exploratory study, we aimed to investigate the putative presence of a uterine microbiome in a selected series of non-pregnant women through deep sequencing of the V1-2 hypervariable region of the 16S ribosomal RNA (rRNA) gene.Methods. Nineteen women with various reproductive conditions, including subfertility, scheduled for hysteroscopy and not showing uterine anomalies were recruited. Subjects were highly diverse with regard to demographic and medical history and included nulliparous and parous women. Endometrial tissue and mucus harvesting was performed by use of a transcervical device designed to obtain endometrial biopsy, while avoiding cervicovaginal contamination. Bacteria were targeted by use of a barcoded Illumina MiSeq paired-end sequencing method targeting the 16S rRNA gene V1-2 region, yielding an average of 41,194 reads per sample after quality filtering. Taxonomic annotation was pursued by comparison with sequences available through the Ribosomal Database Project and the NCBI database.Results. Out of 183 unique 16S rRNA gene amplicon sequences, 15 phylotypes were present in all samples. In some 90% of the women included, community architecture was fairly similar inasmuch B. xylanisolvens, B. thetaiotaomicron, B. fragilis and an undetermined Pelomonas taxon constituted over one third of the endometrial bacterial community. On the singular phylotype level, six women showed predominance of L. crispatus or L. iners in the presence of the Bacteroides core. Two endometrial communities were highly dissimilar, largely lacking the Bacteroides core, one dominated by L. crispatus and another consisting of a highly diverse community, including Prevotella spp., Atopobium vaginae, and Mobiluncus curtisii.Discussion. Our findings are, albeit not necessarily generalizable, consistent with the presence of a unique microbiota dominated by Bacteroides residing on the endometrium of the human non-pregnant uterus. The transcervical sampling approach may be influenced to an unknown extent by endocervical microbiota, which remain uncharacterised, and therefore warrants further validation. Nonetheless, consistent with our understanding of the human microbiome, the uterine microbiota are likely to have a previously unrecognized role in uterine physiology and human reproduction. Further study is therefore warranted to document community ecology and dynamics of the uterine microbiota, as well as the role of the uterine microbiome in health and disease.

ObjectiveBacterial vaginosis (BV), the most common vaginal disorder among women of reproductive age, has been suggested as co-factor in the development of cervical cancer. Previous studies examining the relationship between BV and cervical intra-epithelial neoplasia (CIN) provided inconsistent and conflicting results. The aim of this study is to clarify the association between these two conditions.MethodsA systematic review and meta-analysis were conducted to summarize published literature on the association between BV and cervical pre-cancerous lesions. An extensive search of electronic databases Medline (Pubmed) and Web of Science was performed. The key words ‘bacterial vaginosis’ and ‘bacterial infections and vaginitis’ were used in combination with ‘cervical intraepithelial neoplasia’, ‘squamous intraepithelial lesions’, ‘cervical lesions’, ‘cervical dysplasia’, and ‘cervical screening’. Eligible studies required a clear description of diagnostic methods used for detecting both BV and cervical pre-cancerous lesions. Publications were included if they either reported odds ratios (OR) and corresponding 95% confidence intervals (CI) representing the magnitude of association between these two conditions, or presented data that allowed calculation of the OR.ResultsOut of 329 articles, 17 cross-sectional and 2 incidence studies were selected. In addition, two studies conducted in The Netherlands, using the national KOPAC system, were retained. After testing for heterogeneity and publication bias, meta-analysis and meta-regression were performed, using a random effects model. Although heterogeneity among studies was high (χ2 = 164.7, p<0.01, I2 = 88.5), a positive association between BV and cervical pre-cancerous lesions was found, with an overall estimated odds ratio of 1.51 (95% CI, 1.24–1.83). Meta-regression analysis could not detect a significant difference between studies based on BV diagnosis, CIN diagnosis or study population.ConclusionsAlthough most studies were cross-sectional and heterogeneity was high, this meta-analysis confirms a connection between BV and CIN.