Characterization of the vaginal microflora

The microbial flora of the vagina affects the health of women, their fetuses, and newborns. Conventional culture methods failed to detect some fastidious vaginal bacteria, leading to an incomplete picture of the diversity of the vaginal microflora. DNA-based identification methods have facilitated the detection and identification of bacteria without cultivation, and the advantages and limitations of this approach are described. Recently, molecular studies of the vaginal microflora have discovered several uncultivated bacterial species. An important new insight which stems from our research efforts is the discovery that there is a strong association between bacterial vaginosis and the presence of a thus far unrecognized species, i.e. the strictly anaerobe and very fastidious Gram positive coccus Atopobium vaginae. Also Dialister, Leptotrichia and Megasphaera species were commonly found in women with bacterial vaginosis. Another research group (77) found that several unknown bacteria in the Clostridiales order were found to be highly specific indicators of bacterial vaginosis and suggested that these might be possible candidates for future PCR-based diagnosis of bacterial vaginosis. In addition, the comparison of traditional methods, i.e. microscopy and culture, with DNA-based techniques for characterization of the vaginal microflora have allowed us to refine Gram stain based grading of vaginal smears. We pointed out the presence of sub-categories within what was designated as grade I normal microflora, pinpointed especially a distinct cell type related to Lactobacillus crispatus (grade Ia) and described an additional category (grade I-like) related to the predominant presence of Bifidobacterium spp. Already molecular analysis of bacterial vaginosis-associated bacteria has contributed to the refined described description of normal and disturbed vaginal microflora, but it remains to be seen whether it will succeed in elucidating the etiology of bacterial vaginosis. Our study showed that culture remains essential and the most complete picture of the composition of complex microbial communities is obtained by the combination of culture-based with culture-independent approaches. From the findings during the last five years, it is already obvious that a more complete understanding of vaginal microbial populations will lead to better strategies to maintain healthy vaginal microflora and might create opportunities to explore the role of previously unknown bacteria in reproductive tract diseases

Imbalances between matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) in maternal serum during preterm labor

Background: Matrix metalloproteinases (MMPs) are involved in remodeling of the extracellular matrix (ECM) during pregnancy and parturition. Aberrant ECM degradation by MMPs or an imbalance between MMPs and their tissue inhibitors (TIMPs) have been implicated in the pathogenesis of preterm labor, however few studies have investigated MMPs or TIMPs in maternal serum. Therefore, the purpose of this study was to determine serum concentrations of MMP-3, MMP-9 and all four TIMPs as well as MMP:TIMP ratios during term and preterm labor. Methods: A case control study with 166 singleton pregnancies, divided into four groups: (1) women with preterm birth, delivering before 34 weeks (PTB); (2) gestational age (GA) matched controls, not in preterm labor; (3) women at term in labor and (4) at term not in labor. MMP and TIMP concentrations were measured using Luminex technology. Results: MMP-9 and TIMP-4 concentrations were higher in women with PTB vs. GA matched controls (resp. p = 0.01 and p<0.001). An increase in MMP-9:TIMP-1 and MMP-9:TIMP-2 ratio was observed in women with PTB compared to GA matched controls (resp. p = 0.02 and p<0.001) as well as compared to women at term in labor (resp. p = 0.006 and p<0.001). Multiple regression results with groups recoded as three key covariates showed significantly higher MMP-9 concentrations, higher MMP-9:TIMP-1 and MMP-9:TIMP-2 ratios and lower TIMP-1 and -2 concentrations for preterm labor. Significantly higher MMP-9 and TIMP-4 concentrations and MMP-9:TIMP-2 ratios were observed for labor. Conclusions: Serum MMP-9:TIMP-1 and MMP-9:TIMP-2 balances are tilting in favor of gelatinolysis during preterm labor. TIMP-1 and -2 concentrations were lower in preterm gestation, irrespective of labor, while TIMP-4 concentrations were raised in labor. These observations suggest that aberrant serum expression of MMP:TIMP ratios and TIMPs reflect pregnancy and labor status, providing a far less invasive method to determine enzymes essential in ECM remodeling during pregnancy and parturition

Association between bacterial vaginosis and cervical intraepithelial neoplasia: systematic review and meta-analysis

Objective: Bacterial 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. Methods: A 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 precancerous 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. Results: Out 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 (chi(2) = 164.7, p < 0.01, I-2 = 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. Conclusions: Although most studies were cross-sectional and heterogeneity was high, this meta-analysis confirms a connection between BV and CIN

Longitudinal qPCR study of the dynamics of L. crispatus, L. iners, A. vaginae, (sialidase positive) G. vaginalis, and P. bivia in the vagina

Background: To obtain more detailed understanding of the causes of disturbance of the vaginal microflora (VMF), a longitudinal study was carried out for 17 women during two menstrual cycles. Methods: Vaginal swabs were obtained daily from 17 non-pregnant, menarchal volunteers. For each woman, Gram stains were scored, the quantitative changes of 5 key vaginal species, i.e. Atopobium vaginae, Lactobacillus crispatus, L. iners, (sialidase positive) Gardnerella vaginalis and Prevotella bivia were quantified with qPCR and hydrogen-peroxide production was assessed on TMB+ agar. Results: Women could be divided in 9 subjects with predominantly normal VMF (grades Ia, Ib and Iab, group N) and 8 with predominantly disturbed VMF (grades I-like, II, III and IV, group D). VMF was variable between women, but overall stable for most of the women. Menses were the strongest disturbing factor of the VMF. L. crispatus was present at log7-9 cells/ml in grade Ia, Iab and II VMF, but concentrations declined 100-fold during menses. L. crispatus below log7 cells/ml corresponded with poor H2O2-production. L. iners was present at log 10 cells/ml in grade Ib, II and III VMF. Sialidase negative G. vaginalis strains (average log5 cells/ml) were detected in grade I, I-like and IV VMF. In grade II VMF, predominantly a mixture of both sialidase negative and positive G. vaginalis strains (average log9 cells/ml) were present, and predominantly sialidase positive strains in grade III VMF. The presence of A. vaginae (average log9 cells/ml) coincided with grade II and III VMF. P. bivia (log4-8 cells/ml) was mostly present in grade III vaginal microflora. L. iners, G. vaginalis, A. vaginae and P. bivia all increased around menses for group N women, and as such L. iners was considered a member of disturbed VMF. Conclusions: This qPCR-based study confirms largely the results of previous culture-based, microscopy-based and pyrosequencing-based studies

Longitudinal analysis of the vaginal microflora in pregnancy suggests that L. crispatus promotes the stability of the normal vaginal microflora and that L. gasseri and/or L. iners are more conducive to the occurrence of abnormal vaginal microflora

<p>Abstract</p> <p>Background</p> <p>Despite 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 <it>Lactobacillus </it>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 <it>Lactobacillus </it>index species (determined through culture and molecular analysis with tRFLP).</p> <p>Results</p> <p>From 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 <it>Lactobacillus</it>-dominated vaginal microflora (VMF) during the first trimester, of which 18 had grade Ia (<it>L. crispatus </it>cell morphotypes) VMF (23.4%), 16 grade Iab (<it>L. crispatus </it>and other <it>Lactobacillus </it>cell morphotypes) VMF (20.8%), and 43 grade Ib (non-<it>L. crispatus </it>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-<it>Lactobacillus </it>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 <it>L. gasseri/iners </it>incurred a ten-fold increased risk of conversion to abnormal VMF relative to non-<it>L. gasseri/iners </it>VMF (RR 10.41, 95% CI 1.39–78.12, p = 0.008), whereas normal VMF comprising <it>L. crispatus </it>had a five-fold decreased risk of conversion to abnormal VMF relative to non-<it>L. crispatus </it>VMF (RR 0.20, 95% CI 0.05–0.89, p = 0.04).</p> <p>Conclusion</p> <p>The presence of different <it>Lactobacillus </it>species with the normal vaginal microflora is a major determinant to the stability of this microflora in pregnancy: <it>L. crispatus </it>promotes the stability of the normal vaginal microflora while <it>L. gasseri </it>and/or <it>L. iners </it>predispose to some extent to the occurrence of abnormal vaginal microflora.</p

The significance of Lactobacillus crispatus and L. vaginalis for vaginal health and the negative effect of recent sex: a cross-sectional descriptive study across groups of African women

Background: Women in sub-Saharan Africa are vulnerable to acquiring HIV infection and reproductive tract infections. Bacterial vaginosis (BV), a disruption of the vaginal microbiota, has been shown to be strongly associated with HIV infection. Risk factors related to potentially protective or harmful microbiota species are not known. Methods: We present cross-sectional quantitative polymerase chain reaction data of the Lactobacillus genus, five Lactobacillus species, and three BV-related bacteria (Gardnerella vaginalis, Atopobium vaginae, and Prevotella bivia) together with Escherichia coli and Candida albicans in 426 African women across different groups at risk for HIV. We selected a reference group of adult HIV-negative women at average risk for HIV acquisition and compared species variations in subgroups of adolescents, HIV-negative pregnant women, women engaging in traditional vaginal practices, sex workers and a group of HIV-positive women on combination antiretroviral therapy. We explored the associations between presence and quantity of the bacteria with BV by Nugent score, in relation to several factors of known or theoretical importance. Results: The presence of species across Kenyan, South African and Rwandan women was remarkably similar and few differences were seen between the two groups of reference women in Kenya and South Africa. The Rwandan sex workers and HIV-positive women had the highest Gardnerella vaginalis presence (p = 0.006). Pregnant women had a higher Lactobacillus genus mean log (7.01 genome equivalents (geq)/ml) compared to the reference women (6.08 geq/ml). L. vaginalis (43%) was second to L. iners (81.9%) highly present in women with a normal Nugent score. Recent sexual exposure negatively affected the presence of Lactobacillus crispatus (<0.001), L. vaginalis (p = 0.001), and Lactobacillus genus (p < 0.001). Having more than one sexual partner in the last three months was associated with an increased prevalence of Gardnerella vaginalis (p = 0.044) and L. iners (p = 0.001). Conclusions: Although the composition of species across the studied African countries was similar, the presence of protective species i.e. Lactobacillus crispatus and L. vaginalis in women with a normal Nugent score appeared lower compared to non-African studies. Furthermore, Lactobacillus species were negatively affected by sexual behavioural. Strategies to support protective Lactobacillus species are urgently needed

Characterisation of the vaginal microflora of human immunodeficiency virus (HIV) positive and negative women in a sub-urban population of Kenya

Lactobacilli predominate normal vaginal microflora and are important in maintenance of vaginal health. The current study set out to identify and compare culture isolates of vaginal microflora of human immunodeficiency virus (HIV) positive (HIV+ ) and HIV negative (HIV- ) women at different phases during menstrual cycle from a sub-urban population of Kenya. Seventy four (74) women, 41 HIV+ and 33 HIV- , followed up two consecutive menstrual cycles, had high vaginal swabs taken to prepare Gram stains for six visits and anaerobic cultures for four. All 751 isolates identified by t-DNA polymerase chain reaction (PCR) belong to 51 species. Species cultured more frequently in HIV+ participants were: Lactobacillus jensenii (p=0.01), Lactobacillus iners (p=0.02), Gardnerella vaginalis (p=0.01) and Peptoniphilus lacrimalis (p=0.01). Species cultured more frequently in HIV- women were Dialister micraerophilus (p=0.02) and Streptococcus agalactiae (p=0.04). Lactobacillus predominating both groups were Lactobacilli crispatus, L. jensenii, L. iners and Lactobacilli vaginalis. Bacterial vaginosis (BV) was equally high in HIV+ and HIV- women. Lactobacillus and BV-associated species were cultured more frequently in HIV+ women. Minor species differences were found. Predominant Lactobacillus in culture were L. crispatus, L. iners, L. jensenii and L. vaginalis. These women had lower concentrations of lactobacilli in vaginal microflora than observed in previous studies of Caucasian women

The vaginal microbiota: what have we learned after a decade of molecular characterization?

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