Cultivation-independent analysis of changes in bacterial vaginosis flora following metronidazole treatment

Association of Chlamydia trachomatis burden with the vaginal microbiota, bacterial vaginosis, and metronidazole treatment

Bacterial vaginosis (BV), a dysbiosis of the vaginal microbiota, is a common coinfection with Chlamydia trachomatis (Ct), and BV-associated bacteria (BVAB) and their products have been implicated in aiding Ct evade natural immunity. Here, we determined if a non-optimal vaginal microbiota was associated with a higher genital Ct burden and if metronidazole, a standard treatment for BV, would reduce Ct burden or aid in natural clearance of Ct infection. Cervicovaginal samples were collected from women at enrollment and, if testing positive for Ct infection, at a follow-up visit approximately one week later. Cervical Ct burden was assessed by inclusion forming units (IFU) and Ct genome copy number (GCN), and 16S rRNA gene sequencing was used to determine the composition of the vaginal microbiota. We observed a six-log spectrum of IFU and an eight-log spectrum of GCN in our study participants at their enrollment visit, but BV, as indicated by Amsel's criteria, Nugent scoring, or VALENCIA community state typing, did not predict infectious and total Ct burden, although IFU : GCN increased with Amsel and Nugent scores and in BV-like community state types. Ct burden was, however, associated with the abundance of bacterial species in the vaginal microbiota, negatively with Lactobacillus crispatus and positively with Prevotella bivia. Women diagnosed with BV were treated with metronidazole, and Ct burden was significantly reduced in those who resolved BV with treatment. A subset of women naturally cleared Ct infection in the interim, typified by low Ct burden at enrollment and resolution of BV. Abundance of many BVAB decreased, and Lactobacillus increased, in response to metronidazole treatment, but no changes in abundances of specific vaginal bacteria were unique to women who spontaneously cleared Ct infection.

Integrating compositional and functional content to describe vaginal microbiomes in health and disease

BACKGROUND

A Lactobacillus-dominated vaginal microbiome provides the first line of defense against adverse genital tract health outcomes. However, there is limited understanding of the mechanisms by which the vaginal microbiome modulates protection, as prior work mostly described its composition through morphologic assessment and marker gene sequencing methods that do not capture functional information. To address this gap, we developed metagenomic community state types (mgCSTs) which use metagenomic sequences to describe and define vaginal microbiomes based on both composition and functional potential.

RESULTS

MgCSTs are categories of microbiomes classified using taxonomy and the functional potential encoded in their metagenomes. MgCSTs reflect unique combinations of metagenomic subspecies (mgSs), which are assemblages of bacterial strains of the same species, within a microbiome. We demonstrate that mgCSTs are associated with demographics such as age and race, as well as vaginal pH and Gram stain assessment of vaginal smears. Importantly, these associations varied between mgCSTs predominated by the same bacterial species. A subset of mgCSTs, including three of the six predominated by Gardnerella vaginalis mgSs, as well as mgSs of L. iners, were associated with a greater likelihood of bacterial vaginosis diagnosed by Amsel clinical criteria. This L. iners mgSs, among other functional features, encoded enhanced genetic capabilities for epithelial cell attachment that could facilitate cytotoxin-mediated cell lysis. Finally, we report a mgSs and mgCST classifier for which source code is provided and may be adapted for use by the microbiome research community.

CONCLUSIONS

MgCSTs are a novel and easily implemented approach to reduce the dimension of complex metagenomic datasets while maintaining their functional uniqueness. MgCSTs enable the investigation of multiple strains of the same species and the functional diversity in that species. Future investigations of functional diversity may be key to unraveling the pathways by which the vaginal microbiome modulates the protection of the genital tract. Importantly, our findings support the hypothesis that functional differences between vaginal microbiomes, including those that may look compositionally similar, are critical considerations in vaginal health. Ultimately, mgCSTs may lead to novel hypotheses concerning the role of the vaginal microbiome in promoting health and disease, and identify targets for novel prognostic, diagnostic, and therapeutic strategies to improve women's genital health. Video Abstract.

State of the Art for Diagnosis of Bacterial Vaginosis

Bacterial vaginosis (BV) is the most common cause of vaginal discharge among reproductive-age women. It is associated with multiple adverse health outcomes, including increased risk of acquisition of HIV and other sexually transmitted infections (STIs), in addition to adverse birth outcomes. While it is known that BV is a vaginal dysbiosis characterized by a shift in the vaginal microbiota from protective Lactobacillus species to an increase in facultative and strict anaerobic bacteria, its exact etiology remains unknown. The purpose of this minireview is to provide an updated overview of the range of tests currently used for the diagnosis of BV in both clinical and research settings. This article is divided into two primary sections: traditional BV diagnostics and molecular diagnostics. Molecular diagnostic assays, particularly 16S rRNA gene sequencing, shotgun metagenomic sequencing, and fluorescence in situ hybridization (FISH), are specifically highlighted, in addition to multiplex nucleic acid amplification tests (NAATs), given their increasing use in clinical practice (NAATs) and research studies (16S rRNA gene sequencing, shotgun metagenomic sequencing, and FISH) regarding the vaginal microbiota and BV pathogenesis. We also provide a discussion of the strengths and weaknesses of current BV diagnostic tests and discuss future challenges in this field of research.

Exploring Microbiota Diversity in Cervical Lesion Progression and HPV Infection through 16S rRNA Gene Metagenomic Sequencing

(1) Background: Cervical cancer is a significant health concern, with the main cause being persistent infection with high-risk Human Papillomavirus (hrHPV). There is still no evidence for why viral persistence occurs in some women, but recent studies have revealed the interplay between cervical microbiota and hrHPV. This research aimed to characterize the cervicovaginal microbiota in cervical lesion progression and HPV infection status. (2) Methods: This study included 85 cervical specimens from women from the north-eastern region of Romania. DNA was isolated from cervical secretion for HPV genotyping and 16S ribosomal RNA gene NGS sequencing. (3) Results: Our study revealed a distinct pattern within the studied group when considering Lactobacillus species, which differs from findings reported in other populations. Specifically, the presence of Lactobacillus iners coupled with the absence of Lactobacillus crispatus alongside Atopobium spp., Prevotella spp., and Gardnerella spp. could serve as defining factors for severe cervical lesions. The results also showed a significant association between microbiota diversity, HPV infection, and cervical lesion progression. (4) Conclusions: As the microbiota profile seems to vary among different populations and individuals, a deeper comprehension of its composition has the potential to develop personalized detection and treatment approaches for cervical dysplasia and cancer.

Abrupt perturbation and delayed recovery of the vaginal ecosystem following childbirth

The vaginal ecosystem is closely tied to human health and reproductive outcomes, yet its dynamics in the wake of childbirth remain poorly characterized. Here, we profile the vaginal microbiota and cytokine milieu of participants sampled longitudinally throughout pregnancy and for at least one year postpartum. We show that delivery, regardless of mode, is associated with a vaginal pro-inflammatory cytokine response and the loss of Lactobacillus dominance. By contrast, neither the progression of gestation nor the approach of labor strongly altered the vaginal ecosystem. At 9.5-months postpartum-the latest timepoint at which cytokines were assessed-elevated inflammation coincided with vaginal bacterial communities that had remained perturbed (highly diverse) from the time of delivery. Time-to-event analysis indicated a one-year postpartum probability of transitioning to Lactobacillus dominance of 49.4%. As diversity and inflammation declined during the postpartum period, dominance by L. crispatus, the quintessential health-associated commensal, failed to return: its prevalence before, immediately after, and one year after delivery was 41%, 4%, and 9%, respectively. Revisiting our pre-delivery data, we found that a prior live birth was associated with a lower odds of L. crispatus dominance in pregnant participants-an outcome modestly tempered by a longer ( > 18-month) interpregnancy interval. Our results suggest that reproductive history and childbirth in particular remodel the vaginal ecosystem and that the timing and degree of recovery from delivery may help determine the subsequent health of the woman and of future pregnancies.

Single-Molecule Approach to 16S rRNA for Vaginal Microbiome Signatures in Response to Metronidazole Treatment

Bacterial vaginosis (BV) is the most common infection of the lower reproductive tract among women of reproductive age, characterized by a depletion of health-associated Lactobacillus and an overgrowth of anaerobes. Metronidazole has been recommended as a first-line therapy for treating BV for decades. Although most cases are cured by the treatment, recurrent infections of BV seriously affect women's reproductive health. Until now, limited information on the vaginal microbiota has been explored at the species level. Here, we adopted a single molecular sequencing approach for the 16S rRNA gene, named FLAST (full-length assembly sequencing technology), to analyze the human vaginal microbiota that improved species-level resolution for taxonomy and identified microbiota alterations in the vaginal tract in response to treatment with metronidazole. Appling high-throughput sequencing, we identified 96 and 189 novel full-length 16S rRNA gene sequences in Lactobacillus and Prevotella, respectively, which had not previously been reported in vaginal samples. Moreover, we found that Lactobacillus iners was significantly enriched in the cured group before metronidazole treatment, and that was maintained in a high frequency after the treatment, suggesting an important role for this species in response to metronidazole treatment. Our research also highlights the importance of the single-molecule paradigm for progressing the field of microbiology and applying these insights to better understand the dynamic microbiota during BV treatment. Subsequent novel treatment approaches should be proposed to improve BV treatment outcomes, optimize the vaginal microbiome, and reduce gynecological and obstetric sequelae. IMPORTANCE Bacterial vaginosis (BV) is a common infectious disease of the reproductive tract. Metronidazole treatment, as the first line of treatment, frequently fails at recovery of the microbiome. However, the precise types of Lactobacillus and other bacteria involved in BV remain unclear, and this has resulted in a failure to identify potential markers to predict clinic outcomes. In this study, we adopted a 16S rRNA gene full-length assembly sequencing technology for the taxonomy analysis and evaluation of vaginal microbiota before and after treatment with metronidazole. We additionally identified 96 and 189 novel 16S rRNA gene sequences in Lactobacillus and Prevotella species, respectively, in vaginal samples, which improves our understanding of the vaginal microbiota. Moreover, we found that the abundance of Lactobacillus iners and Prevotella bivia before treatment was associated with a lack of cure. These potential biomarkers will help to facilitate future studies aimed at improving BV treatment outcomes, optimize the vaginal microbiome, and reduce adverse sexual and reproductive outcomes.

High-resolution functional description of vaginal microbiomes in health and disease

Background

A Lactobacillus-dominated vaginal microbiome provides the first line of defense against numerous adverse genital tract health outcomes. However, there is limited understanding of the mechanisms by which the vaginal microbiome modulates protection, as prior work mostly described its composition through morphologic assessment and marker gene sequencing methods that do not capture functional information. To address this limitation, we developed metagenomic community state types (mgCSTs) which uses metagenomic sequences to describe and define vaginal microbiomes based on both composition and function.

Results

MgCSTs are categories of microbiomes classified using taxonomy and the functional potential encoded in their metagenomes. MgCSTs reflect unique combinations of metagenomic subspecies (mgSs), which are assemblages of bacterial strains of the same species, within a microbiome. We demonstrate that mgCSTs are associated with demographics such as age and race, as well as vaginal pH and Gram stain assessment of vaginal smears. Importantly, these associations varied between mgCSTs predominated by the same bacterial species. A subset of mgCSTs, including three of the six predominated by Gardnerella mgSs, as well as a mgSs of L. iners, were associated with a greater likelihood of Amsel bacterial vaginosis diagnosis. This L. iners mgSs, among other functional features, encoded enhanced genetic capabilities for epithelial cell attachment that could facilitate cytotoxin-mediated cell lysis. Finally, we report a mgSs and mgCST classifier as an easily applied, standardized method for use by the microbiome research community.

Conclusions

MgCSTs are a novel and easily implemented approach to reducing the dimension of complex metagenomic datasets, while maintaining their functional uniqueness. MgCSTs enable investigation of multiple strains of the same species and the functional diversity in that species. Future investigations of functional diversity may be key to unraveling the pathways by which the vaginal microbiome modulates protection to the genital tract. Importantly, our findings support the hypothesis that functional differences between vaginal microbiomes, including those that may look compositionally similar, are critical considerations in vaginal health. Ultimately, mgCSTs may lead to novel hypotheses concerning the role of the vaginal microbiome in promoting health and disease, and identify targets for novel prognostic, diagnostic, and therapeutic strategies to improve women's genital health.

Contribution of Lactobacillus iners to Vaginal Health and Diseases: A Systematic Review

Lactobacillus iners, first described in 1999, is a prevalent bacterial species of the vaginal microbiome. As L. iners does not easily grow on de Man-Rogosa-Sharpe agar, but can grow anaerobically on blood agar, it has been initially overlooked by traditional culture methods. It was not until the wide application of molecular biology techniques that the function of L. iners in the vaginal microbiome was carefully explored. L. iners has the smallest genome among known Lactobacilli and it has many probiotic characteristics, but is partly different from other major vaginal Lactobacillus species, such as L. crispatus, in contributing to the maintenance of a healthy vaginal microbiome. It is not only commonly present in the healthy vagina but quite often recovered in high numbers in bacterial vaginosis (BV). Increasing evidence suggests that L. iners is a transitional species that colonizes after the vaginal environment is disturbed and offers overall less protection against vaginal dysbiosis and, subsequently, leads to BV, sexually transmitted infections, and adverse pregnancy outcomes. Accordingly, under certain conditions, L. iners is a genuine vaginal symbiont, but it also seems to be an opportunistic pathogen. Further studies are necessary to identify the exact role of this intriguing species in vaginal health and diseases.

Klebsiella spp. isolates from Houston bayous exhibit increased resistance to lead exposure and possess enhanced virulence potential

Houston watersheds are susceptible to microbial contamination as well as chemical contaminations from bordering industrial facilities. Bacterial loads in various Houston bayous were determined, and pathogenic Gram-negative bacteria were isolated for characterization. Isolates included Klebsiella aerogenes and Klebsiella pneumoniae. To determine whether environmental exposures to lead (Pb), measured in our Houston bayou samples, resulted in bacterial adaptations, we compared growth kinetics, biofilm production, oxidative stress resistance, and eukaryotic co-culture growth of environmentally isolated K. aerogenes and K. pneumoniae to their respective commercially acquired reference strains. Interestingly, the K. aerogenes environmental isolate displayed significantly better growth than the reference strain in the presence of 50 ppb of Pb. Unexpectedly, we did not observe any differences in biofilm production of the aforementioned strains when challenged with a range of Pb (0.5-50 ppb). However, when comparing our K. pneumoniae environmental isolate to its reference strain, there were significantly higher levels of biofilm produced by the environmental isolate when challenged with Pb concentrations of 10 and 50 ppb. When grown in eukaryotic cell co-culture with either BAES 2B lung cells or CCD 841 colon epithelial cells in the presence of 20 ppb Pb, the environmental isolates of K. aerogenes and K. pneumoniae had a significantly higher fold-increase over 6 h than their respective reference strains. Taken together, the environmentally isolated Klebsiella spp. appeared to be more Pb-tolerant than their respective reference strains, a possible environmental adaptation. Such enhanced tolerance can promote environmental persistence and increase the possibility of causing human disease.

To understand the reproductive tract microbiome associated with infertility through metagenomics analysis

Background

Knowledge of the microbiome is in its infancy in health and human illness, especially concerning human reproduction. We will be better able to treat dysbiosis of the reproductive tract clinically if it is better explained and understood. It has been shown that altered vaginal microbiota affects parturition, and its function is uncertain in assisted reproductive technologies. However, the effects of recognized microbes such as Mycoplasma tuberculosis, Chlamydia trachomatis, and Neisseria gonorrhoeae are well established, resulting in subclinical changes which are considered to be risk factors for infertility and poor reproductive outcomes.

Main body

Recent studies indicate that the vaginal tract comprises several different organisms of the microbiome. Some microbiota can play an important role not only in the reproductive tract but also in overall health. The microbiome of the female reproductive tract has been identified mainly based on studies that examine vaginal samples across many reproductive technologies, using a metagenomics approach.

Conclusion

Alteration of reproductive tract microbiota or presence of certain microbiota irrespective of the level of pathogenicity may interfere with fertilization, implantation, and subsequent embryo development. This may lead to failed fertility treatments and reduced live birth rate (LBR).

The Complex Link between the Female Genital Microbiota, Genital Infections, and Inflammation

The female genital tract microbiota is part of a complex ecosystem influenced by several physiological, genetic, and behavioral factors. It is uniquely linked to a woman's mucosal immunity and plays a critical role in the regulation of genital inflammation. A vaginal microbiota characterized by a high abundance of lactobacilli and low overall bacterial diversity is associated with lower inflammation. On the other hand, a more diverse microbiota is linked to high mucosal inflammation levels, a compromised genital epithelial barrier, and an increased risk of sexually transmitted infections and other conditions. Several bacterial taxa such as Gardnerella spp., Prevotella spp., Sneathia spp., and Atopobium spp. are well known to have adverse effects; however, the definitive cause of this microbial dysbiosis is yet to be fully elucidated. The aim of this review is to discuss the multiple ways in which the microbiota influences the overall genital inflammatory milieu and to explore the causes and consequences of this inflammatory response. While there is abundant evidence linking a diverse genital microbiota to elevated inflammation, understanding the risk factors and mechanisms through which it affects genital health is essential. A robust appreciation of these factors is important for identifying effective prevention and treatment strategies.

Lactobacillus iners and gasseri, Prevotella bivia and HPV Belong to the Microbiological Signature Negatively Affecting Human Reproduction

Infertile couples undergoing the use of assisted reproductive technology are a good study model to evaluate the microbiological signatures affecting reproductive health. We tested vaginal lavages, follicular fluids, embryo culture mediums, and seminal fluids from 47 couples for their microbiome composition and HPV infection. Twenty-five infertile couples were diagnosed with unexplained infertility, whereas 22 were diagnosed with explained infertility. Lactobacilli were dominant in the vaginal lavages of both patient groups, and the most abundant species was L. iners (CST III), which is linked to a decreased fertility rate. Besides this, L. gasseri—which is known to be associated with oocyte DNA fragmentation and decreased sperm mobility—was identified in the seminal fluids, follicular fluids, and embryo culture media of the unexplained infertility group. Prevotella was increased in the seminal fluids of the explained infertility group, along with HPV-positive seminal fluids: an infection commonly associated with infertility, especially male infertility. Prevotella has been described to negatively affect sperm motility. Taken together, these results suggest that the profiling of the reproductive tract microbiome can add new perspectives to human reproduction.

Stable and transient structural variation in lemur vaginal, labial and axillary microbiomes: patterns by species, body site, ovarian hormones and forest access

Host-associated microbiomes shape and are shaped by myriad processes that ultimately delineate their symbiotic functions. Whereas a host's stable traits, such as its lineage, relate to gross aspects of its microbiome structure, transient factors, such as its varying physiological state, relate to shorter term, structural variation. Our understanding of these relationships in primates derives principally from anthropoid studies and would benefit from a broader, comparative perspective. We thus examined the vaginal, labial and axillary microbiota of captive, female ring-tailed lemurs (Lemur catta) and Coquerel's sifakas (Propithecus coquereli), across an ovarian cycle, to better understand their relation to stable (e.g. species identity/mating system, body site) and transient (e.g. ovarian hormone concentration, forest access) host features. We used 16S amplicon sequencing to determine microbial composition and enzyme-linked immunosorbent assays to measure serum hormone concentrations. We found marked variation in microbiota diversity and community composition between lemur species and their body sites. Across both host species, microbial diversity was significantly correlated with ovarian hormone concentrations: negatively with progesterone and positively with estradiol. The hosts' differential forest access related to the diversity of environmental microbes, particularly in axillary microbiomes. Such transient endogenous and exogenous modulators have potential implications for host reproductive health and behavioral ecology.

Novel Selective Inhibition of Lactobacillus iners by Lactobacillus-Derived Bacteriocins

Lactobacillus iners is often associated with vaginal dysbiosis and bacterial vaginosis (BV), which are risk factors for adverse gynecological and obstetric outcomes. To discover natural inhibitors of L. iners, cell-free culture supernatants (CFSs) from 77 vaginal human Lactobacillus strains and 1 human intestinal strain were screened for inhibitory activity. Three active strains were identified, and Lactobacillus paragasseri K7 (K7), a human intestinal strain, produced the most potent L. iners-inhibitory activity. The active material was purified from the K7 CFS and yielded three active peptides, identified as components of two different class IIb, two-peptide bacteriocins, gassericin K7A (GasK7A) and gassericin K7B (GasK7B). The peptides corresponded to the GasK7A α peptide and the GasK7B α and β peptides. While all three peptides exhibited individual activity against L. iners, GasK7B α was the most potent, with an MIC of 23 ng/ml (4 nM). When combined in equal amounts, the GasK7B α and β peptides showed synergistic inhibition, with an MIC of 2 ng/ml (each peptide at 0.4 nM). Among the four major vaginal Lactobacillus species, the K7 bacteriocins selectively inhibited L. iners All 21 strains of L. iners tested (100%) were inhibited by the K7 bacteriocins, whereas <20% of the vaginal Lactobacillus crispatus, L. jensenii, and L. gasseri strains were inhibited. The combination of the BV treatment metronidazole and K7 bacteriocins completely killed both L. iners and Gardnerella vaginalis in a coculture experiment to mimic BV conditions. In contrast, this treatment did not inhibit L. crispatus cultures.IMPORTANCELactobacillus iners is a prevalent species of the vaginal microbiome, but unlike other major vaginal Lactobacillus species, it is not considered protective against BV and can coexist with BV-associated bacteria. L. iners is generally the first Lactobacillus species to emerge following the treatment of BV with metronidazole, and mounting evidence suggests that it may contribute to the onset and maintenance of vaginal dysbiosis. The discovery of highly potent bacteriocins that selectively kill L. iners while sparing protective vaginal lactobacilli may provide novel pharmacological tools to better understand the roles of this enigmatic bacterium in vaginal ecology and potentially lead to new and improved therapies for dysbiosis-related conditions such as BV.

Gardnerella and vaginal health: the truth is out there

The human vagina is a dynamic ecosystem in which homeostasis depends on mutually beneficial interactions between the host and their microorganisms. However, the vaginal ecosystem can be thrown off balance by a wide variety of factors. Bacterial vaginosis (BV) is the most common vaginal infection in women of childbearing age but its etiology is not yet fully understood, with different controversial theories being raised over the years. What is generally accepted is that BV is often characterized by a shift in the composition of the normal vaginal microbiota, from a Lactobacillus species dominated microbiota to a mixture of anaerobic and facultative anaerobic bacteria. During BV, a polymicrobial biofilm develops in the vaginal microenvironment, being mainly composed of Gardnerella species. The interactions between vaginal microorganisms are thought to play a pivotal role in the shift from health to disease and might also increase the risk of sexually transmitted infections acquisition. Here, we review the current knowledge regarding the specific interactions that occur in the vaginal niche and discuss mechanisms by which these interactions might be mediated. Furthermore, we discuss the importance of novel strategies to fight chronic vaginal infections.

Evaluation of different culture media to support in vitro growth and biofilm formation of bacterial vaginosis-associated anaerobes

Background

Bacterial vaginosis (BV) is one of the most common vaginal infections worldwide. It is associated with the presence of a dense polymicrobial biofilm on the vaginal epithelium, formed mainly by Gardnerella species. The biofilm also contains other anaerobic species, but little is known about their role in BV development.

Aim

To evaluate the influence of different culture media on the planktonic and biofilm growth of six cultivable anaerobes frequently associated with BV, namely Gardnerella sp., Atopobium vaginae, Lactobacillus iners, Mobiluncus curtisii, Peptostreptococcus anaerobius and Prevotella bivia.

Methods

A total of nine different culture media compositions, including commercially available and chemically defined media simulating genital tract secretions, were tested in this study. Planktonic cultures and biofilms were grown under anaerobic conditions (10% carbon dioxide, 10% helium and 80% nitrogen). Planktonic growth was assessed by optical density measurements, and biofilm formation was quantified by crystal violet staining.

Results

Significant planktonic growth was observed for Gardnerella sp., A. vaginae and L. iners in New York City III broth, with or without ascorbic acid supplementation. Biofilm quantification showed high in vitro biofilm growth for Gardnerella sp., P. anaerobius and P. bivia in almost all culture media excluding Brucella broth. Contrary, only New York City III broth was able to promote biofilm formation for A. vaginae, L. iners and M. curtisii.

Conclusions

Our data demonstrate that New York City III broth relative to the other tested media is the most conducive for future studies addressing polymicrobial biofilms development as this culture medium allowed the formation of significant levels of single-species biofilms.

Variation of the Vaginal Lactobacillus Microbiome in Cytolytic Vaginosis

OBJECTIVE

This pilot study aimed to evaluate whether different microbial compositions cause symptoms in patients with Lactobacillus overgrowth and to investigate the variation in Lactobacillus microbiome in cytolytic vaginosis (CV).

MATERIALS AND METHODS

Lactobacillus species were identified from the vaginal fluid of 70 healthy women and 79 patients with CV using molecular analysis of the 16S rRNA gene. χ and Fisher exact tests were used to compare the isolated rates of Lactobacillus species between the 2 groups. The capabilities of dominant Lactobacillus strain to produce acid in the 2 groups were analyzed by repeated measures analysis of variance.

RESULTS

The isolation of 2 or more Lactobacillus species per vaginal sampling was significantly less common in the CV group (1.3%) compared with the healthy control (HC) group 12.2% (p = .013). Significant differences in Lactobacillus species were observed between the 2 groups (p < .001). Lactobacillus crispatus was more often found in the CV group (88.7%) than in the HC group (56.4%, p < .001). Compared with that in the HC group, the dominant L. crispatus strain in the CV group tended to produce more acid.

CONCLUSIONS

The CV group carried a less diverse Lactobacillus species, vaginally. Lactobacillus crispatus was common to both CV and HC groups but demonstrated enhanced acid-producing capability in the CV group. The pathogenesis of CV may be based, in part, on an overgrowth of L. crispatus with enhanced acid-producing capability.

Changes in the vaginal microbiota following antibiotic treatment for Mycoplasma genitalium, Chlamydia trachomatis and bacterial vaginosis

The human vagina harbor a rich microbiota. The optimal state is dominated by lactobacilli that help to maintain health and prevent various diseases. However, the microbiota may rapidly change to a polymicrobial state that has been linked to a number of diseases. In the present study, the temporal changes of the vaginal microbiota in patients treated for sexually transmitted diseases or bacterial vaginosis (BV) and in untreated controls were studied for 26 days. The patients included 52 women treated with azithromycin, tetracyclines or moxifloxacin for present or suspected infection with Chlamydia trachomatis or Mycoplasma genitalium. Women with concurrent BV were also treated with metronidazole. The controls were 10 healthy women of matching age. The microbiota was analyzed by 16S rRNA gene deep sequencing, specific qPCRs and microscopy. There was generally good correlation between Nugent score and community state type (CST) and qPCR confirmed the sequencing results. By sequencing, more than 600 different taxa were found, but only 33 constituted more than 1 ‰ of the sequences. In both patients and controls the microbiota could be divided into three different community state types, CST-I, CST-III and CST-IV. Without metronidazole, the microbiota remained relatively stable regarding CST although changes were seen during menstrual periods. Administration of metronidazole changed the microbiota from CST-IV to CST-III in approximately 50% of the treated patients. In contrast, the CST was generally unaffected by azithromycin or tetracyclines. In 30% of the BV patients, Gardnerella vaginalis was not eradicated by metronidazole. The majority of women colonized with Ureaplasma parvum remained positive after azithromycin while U. urealyticum was eradicated.

Is Lactobacillus Gram-Positive? A Case Study of Lactobacillus iners

Lactobacillus iners is the most prevalent bacterial species in the human vaginal microbiome, and there have been few reports of its Gram-negative stain appearances despite the fact that the genus Lactobacillus is universally described as Gram-positive. Here, using transmission electron microscopy, we reveal that the thinness of the cell wall (17.39 ± 0.8 nm) gives the Gram-negative stain appearance, which can lead to over-diagnosis of bacterial vaginosis. Moreover, comparative genome analysis identified four genes commonly absent in L.iners genomes that might contribute to this phenotypic difference. We suggest that, along with the several niche-specific attributes identified, this unique feature may contribute to the species’ distinguished capability to thrive as the predominant species in the fluctuating vaginal environment as well.

In vitro characteristics of intravaginal Lactobacilli; why is L. iners detected in abnormal vaginal microbial flora?

PURPOSE

Our purpose is to investigate the reasons why Lactobacillus iners is detected in abnormal vaginal microbial flora.

METHODS

In this study, in vitro characteristics of four type strains (L. crispatus, L. iners, L. gasseri, and L. jensenii) were examined by measuring the growth speed by OD₆₆₀, and acid resistance, with gram stain and Live/Dead stain.

RESULTS

The growth speed was L. gasseri > L. jensenii > L. crispatus > L. iners. Bacterial counts of all Lactobacilli in MRS medium began to decrease at the middle of the log-phase of the growth curve. In addition, L. iners grew to 10⁶ CFU/mL and the others grew to 10⁸ CFU/mL. L. iners was mostly Gram-negative with very short rod, while the others were mostly Gram-positive rods. L. iners was completely killed in the pH 3 medium, however, the others grew (in pH 3 medium) in 1/100 order compared with those in the pH 6 medium.

CONCLUSION

L. iners was not a typical gram-positive long rod Lactobacilli and presented weak acid-resistance. The reasons why L. iners is detected in abnormal vaginal microbial flora were presumed to be due to the unique morphologic and microbiologic characteristics.

An Updated Conceptual Model on the Pathogenesis of Bacterial Vaginosis

Bacterial vaginosis (BV) is the most common cause of vaginal discharge. It is associated with an increased risk of preterm delivery, pelvic inflammatory disease, and an increased risk of acquisition of sexually transmitted infections including human immunodeficiency virus (HIV). The epidemiology of BV supports sexual transmission. However, its etiology remains unknown. At the center of the debate is whether BV is caused by a primary pathogen or a polymicrobial consortium of microorganisms that are sexually transmitted. We previously published a conceptual model hypothesizing that BV is initiated by sexual transmission of Gardnerella vaginalis. Critics of this model have iterated that G. vaginalis is found in virginal women and in sexually active women with a normal vaginal microbiota. In addition, colonization does not always lead to BV. However, recent advances in BV pathogenesis research have determined the existence of 13 different species within the genus Gardnerella. It may be that healthy women are colonized by nonpathogenic Gardnerella species, whereas virulent strains are involved in BV development. Based on our results from a recent prospective study, in addition to an extensive literature review, we present an updated conceptual model for the pathogenesis of BV that centers on the roles of virulent strains of G. vaginalis, as well as Prevotella bivia and Atopobium vaginae.

The Vaginal Microbiome in U.S. Black Women: A Systematic Review

Background: Advancements in next-generation sequencing have allowed for a more complete understanding of the vaginal microbiome and its role in health and disease. The role of race/ethnicity in the composition of the vaginal microbiome and what is deemed normal/healthy microbiome is conflicting. Thus, the purpose of this review is to synthesize research that investigated the vaginal microbiome in Black women in the United States by using advanced 16S analysis. Methods: Searches of Pubmed, Google Scholar, and relevant journals for publications between January 2008 and July 2018 were conducted. Eligibility criteria were that the study: (1) used a molecular technique for sequencing of the vaginal microbiome, (2) reported the microbiome by race/ethnicity that included Black women, and (3) was conducted in the United States. Results: Our review selected 18 manuscripts that met the inclusion criteria for full review. Three themes emerged: the vaginal microbiome in healthy women versus women with bacterial vaginosis (BV); vaginal microbiome considerations in HIV; and vaginal microbiome considerations in preterm labor/birth. Overall, our review found that a majority of Black women (including HIV-positive women) have a Lactobacillus dominant group. Specifically, Lactobacillus iners was the most frequently reported Lactobacillus species. Non-Lactobacillus dominant groups were also reported to be found in healthy asymptomatic Black women. The vaginal microbiome's influence on preterm labor and/or birth among Black women was inconclusive and warrants further investigation. Conclusions: The role that the microbiome plays in health and disease among Black women warrants further research to better elucidate the definition of a healthy versus pathogenic microbiome. The wide variability in methods for BV diagnostics and defining preterm labor/birth are significant limitations that should be considered when conducting comparative studies.

Impact of oral metronidazole treatment on the vaginal microbiota and correlates of treatment failure

BACKGROUND

Metronidazole is the first-line treatment for bacterial vaginosis, but cure rates are suboptimal and recurrence rates high.

OBJECTIVES

To evaluate the impact of a standard course of oral metronidazole treatment (500 mg twice per day for 7 days) on the vaginal microbiota of Rwandan bacterial vaginosis patients using microscopy and 16S rRNA gene sequencing, and to evaluate correlates of treatment failure.

STUDY DESIGN

HIV-negative, nonpregnant women aged 18-45 years with bacterial vaginosis and/or Trichomonas vaginalis (N=68) were interviewed and sampled before and after metronidazole treatment. They were also screened, and treated if applicable, for other urogenital infections. The vaginal microbiota was assessed by Gram stain Nugent scoring, Illumina 16S rRNA HiSeq sequencing (relative abundances), and BactQuant 16S gene quantitative polymerase chain reaction (estimated concentrations). Only women with a pretreatment Nugent score of 7-10 and a valid posttreatment Nugent score (N=55) were included in metronidazole treatment failure analyses, with treatment failure defined as a posttreatment Nugent score of 4-10.

RESULTS

The bacterial vaginosis cure rate by Nugent scoring was 54.5%. The mean total vaginal bacterial concentration declined from 6.59 to 5.85 log10/μL (P<.001), which was mostly due to a reduction in mean bacterial vaginosis-associated anaerobes concentration (all bacterial vaginosis-associated anaerobe taxa combined) from 6.23 to 4.55 log10/μL (P<.001). However, only 16.4% of women had a bacterial vaginosis anaerobes concentration reduction of more than 50%, and only 3 women had complete eradication. The mean concentration of lactobacilli (all species combined) increased from 4.98 to 5.56 log10/μL (P=.017), with L. iners being the most common species pre- and posttreatment. The mean concentration of pathobionts (defined as Proteobacteria, streptococci, staphylococci, enterococci, and a few others) did not change significantly: from 1.92 log10/μL pretreatment to 2.01 log10/μL posttreatment (P=.939). Pretreatment pathobionts concentration, and having a pretreatment vaginal microbiota type containing more than 50% Gardnerella vaginalis (compared with less than 50%), were associated with increased likelihood of treatment failure, but the latter did not reach statistical significance (P=.044 and P=.084, respectively).

CONCLUSIONS

Metronidazole alone may not cure women with high G. vaginalis relative abundance, potentially due to biofilm presence, and women with high pathobionts concentration. These women may benefit from additional biofilm-disrupting and/or pathobiont-targeting treatments.

Association between the vaginal microbiota, menopause status, and signs of vulvovaginal atrophy

OBJECTIVE

The vaginal microbiota helps protect the female genital tract from disease. We sought to describe the composition of the vaginal microbiota in premenopausal, perimenopausal, and postmenopausal women and to explore the association between the microbiota and vulvovaginal atrophy (VVA).

METHODS

Eighty-seven women (aged 35-60 y) were classified as premenopausal (n = 30), perimenopausal (n = 29), or postmenopausal (n = 28) according to Stages of Reproductive Aging Workshop guidelines. Midvaginal bacterial community composition was characterized by 16S ribosomal RNA gene analysis.

RESULTS

Bacterial communities clustered into six community state types (CSTs), of which four were dominated by Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus iners, or Lactobacillus jensenii, and two (CST IV-A and CST IV-B) had low relative abundance of Lactobacillus. CST IV-A was characterized by Streptococcus and Prevotella, whereas CST IV-B was characterized by Atopobium. There were significant associations between menopause stage and CST (P = 0.004) and between VVA and CST (P = 0.002). Perimenopausal women were more likely to be classified as CST IV-A or L. gasseri CST, whereas postmenopausal women were often classified as CST IV-A. CSTs dominated by L. crispatus and L. iners were more prevalent in premenopausal women. Nineteen participants had signs of mild or moderate VVA. Compared with women with no VVA, the vaginal microbiota of women with mild or moderate atrophy had 25-fold greater odds of being classified as CST IV-A versus L. crispatus CST (adjusted odds ratio, 25.89; 95% credible interval, 2.98-406.79).

CONCLUSIONS

A distinct bacterial community state (CST IV-A) with a low relative abundance of Lactobacillus is associated with VVA. Future studies recruiting a larger number of women are needed to replicate the findings. This study provides an impetus for future longitudinal studies designed to manage, modulate, and restore vaginal microbiota homeostasis, which would provide stronger evidence for a causal relationship with VVA and ultimately improve the treatment and prevention of atrophic vaginitis in menopause.

Associations between sexual habits, menstrual hygiene practices, demographics and the vaginal microbiome as revealed by Bayesian network analysis

The vaginal microbiome plays an influential role in several disease states in reproductive age women, including bacterial vaginosis (BV). While demographic characteristics are associated with differences in vaginal microbiome community structure, little is known about the influence of sexual and hygiene habits. Furthermore, associations between the vaginal microbiome and risk symptoms of bacterial vaginosis have not been fully elucidated. Using Bayesian network (BN) analysis of 16S rRNA gene sequence results, demographic and extensive questionnaire data, we describe both novel and previously documented associations between habits of women and their vaginal microbiome. The BN analysis approach shows promise in uncovering complex associations between disparate data types. Our findings based on this approach support published associations between specific microbiome members (e.g., Eggerthella, Gardnerella, Dialister, Sneathia and Ruminococcaceae), the Nugent score (a BV diagnostic) and vaginal pH (a risk symptom of BV). Additionally, we found that several microbiome members were directly connected to other risk symptoms of BV (such as vaginal discharge, odor, itch, irritation, and yeast infection) including L. jensenii, Corynebacteria, and Proteobacteria. No direct connections were found between the Nugent Score and risk symptoms of BV other than pH, indicating that the Nugent Score may not be the most useful criteria for assessment of clinical BV. We also found that demographics (i.e., age, ethnicity, previous pregnancy) were associated with the presence/absence of specific vaginal microbes. The resulting BN revealed several as-yet undocumented associations between birth control usage, menstrual hygiene practices and specific microbiome members. Many of these complex relationships were not identified using common analytical methods, i.e., ordination and PERMANOVA. While these associations require confirmatory follow-up study, our findings strongly suggest that future studies of the vaginal microbiome and vaginal pathologies should include detailed surveys of participants' sanitary, sexual and birth control habits, as these can act as confounders in the relationship between the microbiome and disease. Although the BN approach is powerful in revealing complex associations within multidimensional datasets, the need in some cases to discretize the data for use in BN analysis can result in loss of information. Future research is required to alleviate such limitations in constructing BN networks. Large sample sizes are also required in order to allow for the incorporation of a large number of variables (nodes) into the BN, particularly when studying associations between metadata and the microbiome. We believe that this approach is of great value, complementing other methods, to further our understanding of complex associations characteristic of microbiome research.

Combined oral and topical antimicrobial therapy for male partners of women with bacterial vaginosis: Acceptability, tolerability and impact on the genital microbiota of couples - A pilot study

Objectives

Recurrence following recommended treatment for bacterial vaginosis is unacceptably high. While the pathogenesis of recurrence is not well understood, recent evidence indicates re-infection from sexual partners is likely to play a role. The aim of this study was to assess the acceptability and tolerability of topical and oral antimicrobial therapy in male partners of women with bacterial vaginosis (BV), and to investigate the impact of dual-partner treatment on the vaginal and penile microbiota.

Methods

Women with symptomatic BV (Nugent Score of 4–10 and ≥3 Amsel criteria) and their regular male sexual partner were recruited from Melbourne Sexual Health Centre, Melbourne, Australia. Women received oral metronidazole 400mg twice daily (or intra-vaginal 2% clindamycin cream, if contraindicated) for 7-days. Male partners received oral metronidazole 400mg twice daily and 2% clindamycin cream topically to the penile skin twice daily for 7-days. Couples provided self-collected genital specimens and completed questionnaires at enrolment and then weekly for 4-weeks. Genital microbiota composition was determined by 16S rRNA gene sequencing. Changes in genital microbiota composition were assessed by Bray-Curtis index. Bacterial diversity was measured by the Shannon Diversity Index.

Results

Twenty-two couples were recruited. Sixteen couples (76%) completed all study procedures. Adherence was high; most participants took >90% of prescribed medication. Medication, and particularly topical clindamycin in males, was well tolerated. Dual-partner treatment had an immediate and sustained effect on the composition of vaginal microbiota (median Bray-Curtis score day 0 versus day 8 = 0.03 [IQR 0–0.15], day 0 vs day 28 = 0.03 [0.02–0.11]). We observed a reduction in bacterial diversity of the vaginal microbiota and a decrease in the prevalence and abundance of BV-associated bacteria following treatment. Treatment had an immediate effect on the composition of the cutaneous penile microbiota (median Bray-Curtis score day 0 vs day 8 = 0.09 [0.04–0.17]), however this was not as pronounced at day 28 (median Bray-Curtis score day 0 vs day 28 = 0.38 [0.11–0.59]). A decrease in the prevalence and abundance of BV-associated bacteria in the cutaneous penile microbiota was observed immediately following treatment at day 8.

Conclusion

Combined oral and topical treatment of male partners of women with BV is acceptable and well tolerated. The combined acceptability and microbiological data presented in this paper supports the need for larger studies with longer follow up to characterize the sustained effect of dual partner treatment on the genital microbiota of couples and assess the impact on BV recurrence.

Lactobacillus iners, the unusual suspect

Lactobacillus iners is an unusual Lactobacillus species which does not grow on de Man Rogosa Sharpe agar, does not produce d-lactic acid, and only limited amounts of hydrogen peroxide. Its production of inerolysin, a cytotoxin, is also unusual for a lactobacillus. Epidemiological studies point to an ambiguous role for this species, which is quite often recovered in high numbers from vaginal dysbiosis and offers limited protection against vaginal dysbiosis and, subsequently, against sexually transmitted infections and adverse pregnancy outcome. Several data indicate that L. iners might even contribute to the onset and maintenance of vaginal dysbiosis and be a risk factor for adverse pregnancy outcome.

Vaginal ecosystem modeling of growth patterns of anaerobic bacteria in microaerophilic conditions

The human vagina constitutes a complex ecosystem created through relationships established between host mucosa and bacterial communities. In this ecosystem, classically defined bacterial aerobes and anaerobes thrive as communities in the microaerophilic environment. Levels of CO₂ and O₂ present in the vaginal lumen are impacted by both the ecosystem's physiology and the behavior and health of the human host. Study of such complex relationships requires controlled and reproducible causational approaches that are not possible in the human host that, until recently, was the only place these bacterial communities thrived. To address this need we have utilized our ex vivo human vaginal mucosa culture system to support controlled, reproducible colonization by vaginal bacterial communities (VBC) collected from healthy, asymptomatic donors. Parallel vaginal epithelial cells (VEC)-VBC co-cultures were exposed to two different atmospheric conditions to study the impact of CO₂ concentrations upon the anaerobic bacteria associated with dysbiosis and inflammation. Our data suggest that in the context of transplanted VBC, increased CO₂ favored specific lactobacilli species defined as microaerophiles when grown as monocultures. In preliminary studies, the observed community changes also led to shifts in host VEC phenotypes with significant changes in the host transcriptome, including altered expression of select molecular transporter genes. These findings support the need for additional study of the environmental changes associated with behavior and health upon the symbiotic and adversarial relationships that are formed in microbial communities present in the human vaginal ecosystem.

Etiology of bacterial vaginosis and polymicrobial biofilm formation

Microorganisms in nature rarely exist in a planktonic form, but in the form of biofilms. Biofilms have been identified as the cause of many chronic and persistent infections and have been implicated in the etiology of bacterial vaginosis (BV). Bacterial vaginosis is the most common form of vaginal infection in women of reproductive age. Similar to other biofilm infections, BV biofilms protect the BV-related bacteria against antibiotics and cause recurrent BV. In this review, an overview of BV-related bacteria, conceptual models and the stages involved in the polymicrobial BV biofilm formation will be discussed.

The interaction between vaginal microbiota, cervical length, and vaginal progesterone treatment for preterm birth risk

BACKGROUND

Preterm birth is the primary cause of infant death worldwide. A short cervix in the second trimester of pregnancy is a risk factor for preterm birth. In specific patient cohorts, vaginal progesterone reduces this risk. Using 16S rRNA gene sequencing, we undertook a prospective study in women at risk of preterm birth (n = 161) to assess (1) the relationship between vaginal microbiota and cervical length in the second trimester and preterm birth risk and (2) the impact of vaginal progesterone on vaginal bacterial communities in women with a short cervix.

RESULTS

Lactobacillus iners dominance at 16 weeks of gestation was significantly associated with both a short cervix <25 mm (n = 15, P < 0.05) and preterm birth <34⁺⁰ weeks (n = 18; P < 0.01; 69% PPV). In contrast, Lactobacillus crispatus dominance was highly predictive of term birth (n = 127, 98% PPV). Cervical shortening and preterm birth were not associated with vaginal dysbiosis. A longitudinal characterization of vaginal microbiota (<18, 22, 28, and 34 weeks) was then undertaken in women receiving vaginal progesterone (400 mg/OD, n = 25) versus controls (n = 42). Progesterone did not alter vaginal bacterial community structure nor reduce L. iners-associated preterm birth (<34 weeks).

CONCLUSIONS

L. iners dominance of the vaginal microbiota at 16 weeks of gestation is a risk factor for preterm birth, whereas L. crispatus dominance is protective against preterm birth. Vaginal progesterone does not appear to impact the pregnancy vaginal microbiota. Patients and clinicians who may be concerned about "infection risk" associated with the use of a vaginal pessary during high-risk pregnancy can be reassured.

Lactobacillus iners: Friend or Foe?

The vaginal microbial community is typically characterized by abundant lactobacilli. Lactobacillus iners, a fairly recently detected species, is frequently present in the vaginal niche. However, the role of this species in vaginal health is unclear, since it can be detected in normal conditions as well as during vaginal dysbiosis, such as bacterial vaginosis, a condition characterized by an abnormal increase in bacterial diversity and lack of typical lactobacilli. Compared to other Lactobacillus species, L. iners has more complex nutritional requirements and a Gram-variable morphology. L. iners has an unusually small genome (ca. 1 Mbp), indicative of a symbiotic or parasitic lifestyle, in contrast to other lactobacilli that show niche flexibility and genomes of up to 3-4 Mbp. The presence of specific L. iners genes, such as those encoding iron-sulfur proteins and unique σ-factors, reflects a high degree of niche specification. The genome of L. iners strains also encodes inerolysin, a pore-forming toxin related to vaginolysin of Gardnerella vaginalis. Possibly, this organism may have clonal variants that in some cases promote a healthy vagina, and in other cases are associated with dysbiosis and disease. Future research should examine this friend or foe relationship with the host.

Genomic Comparisons of Lactobacillus crispatus and Lactobacillus iners Reveal Potential Ecological Drivers of Community Composition in the Vagina

Lactobacillus crispatus and Lactobacillus iners are common inhabitants of the healthy human vagina. These two species are closely related and are thought to perform similar ecological functions in the vaginal environment. Temporal data on the vaginal microbiome have shown that nontransient instances of cooccurrence are uncommon, while transitions from an L. iners-dominated community to one dominated by L. crispatus, and vice versa, occur often. This suggests that there is substantial overlap in the fundamental niches of these species. Given this apparent niche overlap, it is unclear how they have been maintained as common inhabitants of the human vagina. In this study, we characterized and compared the genomes of L. iners and L. crispatus to gain insight into possible mechanisms driving the maintenance of this species diversity. Our results highlight differences in the genomes of these two species that may facilitate the partitioning of their shared niche space. Many of the identified differences may impact the protective benefits provided to the host by these two species.

IMPORTANCE

The microbial communities that inhabit the human vagina play a critical role in the maintenance of vaginal health through the production of lactic acid and lowering the environmental pH. This precludes the growth of nonindigenous organisms and protects against infectious disease. The two most common types of vaginal communities are dominated by either Lactobacillus iners or Lactobacillus crispatus, while some communities alternate between the two over time. We combined ecological theory with state-of-the-art genome analyses to characterize how these two species might partition their shared niche space in the vagina. We show that the genomes of L. iners and L. crispatus differ in many respects, several of which may drive differences in their competitive abilities in the vagina. Our results provide insight into factors that drive the complicated temporal dynamics of the vaginal microbiome and demonstrate how closely related microbial species partition shared fundamental niche space.

The vaginal microbiota, human papillomavirus infection and cervical intraepithelial neoplasia: what do we know and where are we going next?

The vaginal microbiota plays a significant role in health and disease of the female reproductive tract. Next-generation sequencing techniques based upon the analysis of bacterial 16S rRNA genes permit in-depth study of vaginal microbial community structure to a level of detail not possible with standard culture-based microbiological techniques. The human papillomavirus (HPV) causes both cervical intraepithelial neoplasia (CIN) and cervical cancer. Although the virus is highly prevalent, only a small number of women have a persistent HPV infection and subsequently develop clinically significant disease. There is emerging evidence which leads us to conclude that increased diversity of vaginal microbiota combined with reduced relative abundance of Lactobacillus spp. is involved in HPV acquisition and persistence and the development of cervical precancer and cancer. In this review, we summarise the current literature and discuss potential mechanisms for the involvement of vaginal microbiota in the evolution of CIN and cervical cancer. The concept of manipulation of vaginal bacterial communities using pre- and probiotics is also discussed as an exciting prospect for the field of cervical pathology.

Lactobacillus fermentum ATCC 23271 Displays In vitro Inhibitory Activities against Candida spp

Lactobacilli are involved in the microbial homeostasis in the female genital tract. Due to the high prevalence of many bacterial diseases of the female genital tract and the resistance of microorganisms to various antimicrobial agents, alternative means to control these infections are necessary. Thus, this study aimed to evaluate the probiotic properties of well-characterized Lactobacillus species, including L. acidophilus (ATCC 4356), L. brevis (ATCC 367), L. delbrueckii ssp. delbrueckii (ATCC 9645), L. fermentum (ATCC 23271), L. paracasei (ATCC 335), L. plantarum (ATCC 8014), and L. rhamnosus (ATCC 9595), against Candida albicans (ATCC 18804), Neisseria gonorrhoeae (ATCC 9826), and Streptococcus agalactiae (ATCC 13813). The probiotic potential was investigated by using the following criteria: (i) adhesion to host epithelial cells and mucus, (ii) biofilm formation, (iii) co-aggregation with bacterial pathogens, (iv) inhibition of pathogen adhesion to mucus and HeLa cells, and (v) antimicrobial activity. Tested lactobacilli adhered to mucin, co-aggregated with all genital microorganisms, and displayed antimicrobial activity. With the exception of L. acidophilus and L. paracasei, they adhered to HeLa cells. However, only L. fermentum produced a moderate biofilm and a higher level of co-aggregation and mucin binding. The displacement assay demonstrated that all Lactobacillus strains inhibit C. albicans binding to mucin (p < 0.001), likely due to the production of substances with antimicrobial activity. Clinical isolates belonging to the most common Candida species associated to vaginal candidiasis were inhibited by L. fermentum. Collectively, our data suggest that L. fermentum ATCC 23271 is a potential probiotic candidate, particularly to complement candidiasis treatment, since presented with the best probiotic profile in comparison with the other tested lactobacilli strains.

Identification of vaginal bacteria diversity and it's association with clinically diagnosed bacterial vaginosis by denaturing gradient gel electrophoresis and correspondence analysis

Bacterial vaginosis (BV) is a common complex associated with numerous adverse health outcomes, affecting women of different ages throughout the world. The etiology of BV remains poorly understood due to the difficulty of establishing a molecular genetic criterion to recognize the vaginal microbiota of BV-positive women from that of the normal women. We used techniques of broad-range PCR-DGGE and gel imaging analysis system cooperated with 16S rRNA gene sequencing and statistical analysis to investigate the community structure of the healthy and BV-affected vaginal microbial ecosystems. The community of vaginal bacteria detected in subjects with BV was far more luxuriant and diverse than in subjects without BV. The mean number of microbial species in 128 BV-positive women was nearly two times greater than in 68 subjects without BV(4.05±1.96 versus 2.59±1.14). Our sequencing efforts yielded many novel phylotypes (198 of our sequences represented 59 species), including several novel BV-associated bacteria (BVAB) and many belonging to opportunistic infections, which remain inexplicable for their roles in determining the health condition of vaginal microflora. This study identifies Algoriphagus aquatilis, Atopobium vaginae, Burkholderia fungorum, Megasphaera genomosp species as indicators to BV and subjects with BV harbor particularly taxon-rich and diverse bacterial communities. Maybe Bifidobacterium, Staphylococcus or even more alien species are commensal creatures in normal vaginal microbiota.

Lactobacillus species as biomarkers and agents that can promote various aspects of vaginal health

The human body is colonized by a vast number of microorganisms collectively referred to as the human microbiota. One of the main microbiota body sites is the female genital tract, commonly dominated by Lactobacillus spp., in approximately 70% of women. Each individual species can constitute approximately 99% of the ribotypes observed in any individual woman. The most frequently isolated species are Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus jensenii and Lactobacillus iners. Residing at the port of entry of bacterial and viral pathogens, the vaginal Lactobacillus species can create a barrier against pathogen invasion since mainly products of their metabolism secreted in the cervicovaginal fluid can play an important role in the inhibition of bacterial and viral infections. Therefore, a Lactobacillus-dominated microbiota appears to be a good biomarker for a healthy vaginal ecosystem. This balance can be rapidly altered during processes such as menstruation, sexual activity, pregnancy and various infections. An abnormal vaginal microbiota is characterized by an increased diversity of microbial species, leading to a condition known as bacterial vaginosis. Information on the vaginal microbiota can be gathered from the analysis of cervicovaginal fluid, by using the Nugent scoring or the Amsel's criteria, or at the molecular level by investigating the number and type of Lactobacillus species. However, when translating this to the clinical setting, it should be noted that the absence of a Lactobacillus-dominated microbiota does not appear to directly imply a diseased condition or dysbiosis. Nevertheless, the widely documented beneficial role of vaginal Lactobacillus species demonstrates the potential of data on the composition and activity of lactobacilli as biomarkers for vaginal health. The substantiation and further validation of such biomarkers will allow the design of better targeted probiotic strategies.

Rapid and Profound Shifts in the Vaginal Microbiota Following Antibiotic Treatment for Bacterial Vaginosis

BACKGROUND

Bacterial vaginosis (BV) is a common polymicrobial disease associated with numerous negative reproductive health outcomes, including an increased risk of human immunodeficiency virus acquisition. BV is treatable with antibiotics, but relapse is common. A more detailed understanding of bacterial dynamics during antibiotic therapy for BV could identify conditions that favor establishment, maintenance, and eradication of BV-associated bacterial species, thereby improving treatment outcomes.

METHODS

We used mathematical models to analyze daily quantitative measurements of 11 key bacterial species during metronidazole treatment for 15 cases of BV.

RESULTS

We identified complete reorganization of vaginal bacterial composition within a day of initiating therapy. Although baseline bacterial levels predicted a longer time to clearance, all anaerobic species were eliminated rapidly within a median of 3 days. However, reemergence of BV-associated species was common following treatment cessation. Gardnerella vaginalis, a facultative anaerobe, was cleared more slowly than anaerobic BV-associated species, and levels of G. vaginalis often rebounded during treatment. We observed gradual Lactobacillus species growth, indicating that untargeted microbes fill the transient vacuum formed during treatment.

CONCLUSIONS

Under antibiotic pressure, the human microbiome can undergo rapid shifts on a scale of hours. When treatment is stopped, BV-associated bacteria quickly reemerge, suggesting a possible role for intermittent prophylactic treatment.

Association between the vaginal microbiota, menopause status, and signs of vulvovaginal atrophy

OBJECTIVE

The vaginal microbiota helps protect the female genital tract from disease. We sought to describe the composition of the vaginal microbiota in premenopausal, perimenopausal, and postmenopausal women and to explore the association between the microbiota and vulvovaginal atrophy (VVA).

METHODS

Eighty-seven women (aged 35-60 y) were classified as premenopausal (n = 30), perimenopausal (n = 29), or postmenopausal (n = 28) according to Stages of Reproductive Aging Workshop guidelines. Midvaginal bacterial community composition was characterized by 16S ribosomal RNA gene analysis.

RESULTS

Bacterial communities clustered into six community state types (CSTs), of which four were dominated by Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus iners, or Lactobacillus jensenii, and two (CST IV-A and CST IV-B) had low relative abundance of Lactobacillus. CST IV-A was characterized by Streptococcus and Prevotella, whereas CST IV-B was characterized by Atopobium. There were significant associations between menopause stage and CST (P = 0.004) and between VVA and CST (P = 0.002). Perimenopausal women were more likely to be classified as CST IV-A or L. gasseri CST, whereas postmenopausal women were often classified as CST IV-A. CSTs dominated by L. crispatus and L. iners were more prevalent in premenopausal women. Nineteen participants had signs of mild or moderate VVA. Compared with women with no VVA, the vaginal microbiota of women with mild or moderate atrophy had 25-fold greater odds of being classified as CST IV-A versus L. crispatus CST (adjusted odds ratio, 25.89; 95% credible interval, 2.98-406.79).

CONCLUSIONS

A distinct bacterial community state (CST IV-A) with a low relative abundance of Lactobacillus is associated with VVA. Future studies recruiting a larger number of women are needed to replicate the findings. This study provides an impetus for future longitudinal studies designed to manage, modulate, and restore vaginal microbiota homeostasis, which would provide stronger evidence for a causal relationship with VVA and ultimately improve the treatment and prevention of atrophic vaginitis in menopause.

Homogeneity of the vaginal microbiome at the cervix, posterior fornix, and vaginal canal in pregnant Chinese women

The vaginal microbiome is an emerging concern in prenatal health. Because the sampling process of vaginal microbiota may pose potential risks for pregnant women, the choice of sampling site should be carefully considered. However, whether the microbial diversity is different across various sampling sites has been controversial. In the present study, three repeated swabs were collected at the cervix (C), posterior fornix (P), and vaginal canal (V) from 34 Chinese women during different pregnancy stages, and vaginal species were determined using the Illumina sequencing of 16S rRNA tag sequences. The identified microbiomes were classified into four community state types (CSTs): CST I (dominated by L. crispatus), CST II (dominated by L. gasseri), CST III (dominated by L. iners), and CST IV-A (characterized by a low abundance of Lactobacillus, but with proportions of various species previously shown to be associated with bacterial vaginosis). All individuals had consistent CST at the three sampling sites regardless of pregnancy stage and CST group. In addition, there was little heterogeneity across community structures within each individual, as determined by LEfSe, indicating high vaginal microbiome homogeneity at the three sampling sites. The present study also revealed different beta diversity during pregnancy stages. The vaginal microbiome variation among women during trimester T1 (9 ± 2.6 weeks) is larger than that of non-pregnant women and women from other trimesters, as demonstrated by the UniFrac distance (P < 0.05). In particular, the present study is the first one that demonstrates the notably difference of vaginal microbiome of postpartum women compare to women in gestation. These results will be useful for future studies of the vaginal microbiota during pregnancy.

High Atopobium vaginae and Gardnerella vaginalis vaginal loads are associated with preterm birth

BACKGROUND

Bacterial vaginosis is a risk factor for preterm birth. The various conventional methods for its diagnosis are laborious and not easily reproducible. Molecular quantification methods have been reported recently, but the specific risk factors they might identify remain unclear.

METHODS

A prospective multicenter national study included pregnant women at risk of preterm birth. A quantitative molecular tool using a specific real-time polymerase chain reaction assay and serial dilutions of a plasmid suspension quantified Atopobium vaginae, Gardnerella vaginalis, lactobacilli, Mycoplasma hominis, and the human albumin gene (for quality control).

RESULTS

In 813 pregnancies, high vaginal loads of either or both of A. vaginae and G. vaginalis were associated with preterm birth (hazard ratio [HR], 3.9; 95% confidence interval {CI}, 1.1-14.1; P = .031). A high vaginal load of A. vaginae was significantly associated with shortened time to delivery and therefore pregnancy length. These times were, respectively, 152.2 and 188.2 days (HR, 5.6; 95% CI, 1.5-21.3; P < .001) before 22 weeks, 149.0 and 183.2 days (HR, 2.8; 95% CI, 1.1-8.2; P = .048) before 28 weeks, and 132.6 and 170.4 days (HR, 2.2; 95% CI, 1.1-4.6; P = .033) before 32 weeks. After multivariate analysis, A. vaginae levels ≥10(8) copies/mL remained significantly associated with delivery before 22 weeks of gestation (adjusted HR, 4.7; 95% CI, .2-17.6; P = .014).

CONCLUSIONS

High vaginal loads of A. vaginae and G. vaginalis are associated with late miscarriage and prematurity in high-risk pregnancies. A high vaginal load of A. vaginae (DNA level ≥10(8) copies/mL) identifies a population at high risk of preterm birth. Further studies that both screen for and then treat A. vaginae are needed.

CLINICAL TRIALS REGISTRATION

NCT00484653.

Longitudinal analysis of vaginal microbiome dynamics in women with recurrent bacterial vaginosis: recognition of the conversion process

Bacterial vaginosis (BV) affects ∼ 30% of women of reproductive age, has a high rate of recurrence, and is associated with miscarriage, preterm birth, and increased risk of acquiring other sexually transmitted infections, including HIV-1. Little is known of the daily changes in the vaginal bacterial composition as it progresses from treatment to recurrence, or whether any of these might be useful in its prediction or an understanding of its causes. We used phylogenetic branch-inclusive quantitative PCR (PB-qPCR) and Lactobacillus blocked/unblocked qPCR (Lb-qPCR) to characterize longitudinal changes in the vaginal microbiota in sequential vaginal self-swabs from five women with recurrent BV, from diagnosis through remission to recurrence. Both patients with acute BV samples dominated by G. vaginalis recurred during the study with similar profiles, whereas the three patients with acute BV samples dominated by other anaerobes did not recur or recurred to an intermediate Nugent score. L. iners dominated remission phases, with intermittent days of abnormal microbial profiles typically associated with menses. The exception was a newly discovered phenomenon, a sustained period of abnormal profiles, termed conversion, which preceded symptomatic acute BV. Species known to have antagonistic activity towards Lactobacillus were detected in pre-conversion samples, possibly contributing to the decline in Lactobacillus. Lb-qPCR scores define two categories of response in the initial post-treatment visit samples; scores <5 may correspond with poor response to treatment or rapid recurrence, whereas scores >8 may predict delayed or no recurrence. Amsel criteria or Nugent scores did not have this potential predictive capability. Larger studies are warranted to evaluate the prognostic potential of detecting conversion and poor Lb-qPCR scores at the post-treatment visit of recurrent BV patients.

Characterization of the vaginal microbiota among sexual risk behavior groups of women with bacterial vaginosis

BACKGROUND

The pathogenesis of bacterial vaginosis (BV) remains elusive. BV may be more common among women who have sex with women (WSW). The objective of this study was to use 454 pyrosequencing to investigate the vaginal microbiome of WSW, women who have sex with women and men (WSWM), and women who have sex with men (WSM) with BV to determine if there are differences in organism composition between groups that may inform new hypotheses regarding the pathogenesis of BV.

METHODS

Vaginal swab specimens from eligible women with BV at the Mississippi State Department of Health STD Clinic were used. After DNA extraction, 454 pyrosequencing of PCR-amplified 16S rRNA gene sequences was performed. Sequence data was classified using the Ribosomal Database Program classifer. Complete linkage clustering analysis was performed to compare bacterial community composition among samples. Differences in operational taxonomic units with an abundance of ≥ 2% between risk behavior groups were determined. Alpha and beta diversity were measured using Shannon's Index implemented in QIIME and Unifrac analysis, respectively.

RESULTS

33 WSW, 35 WSWM, and 44 WSM were included. The vaginal bacterial communities of all women clustered into four taxonomic groups with the dominant taxonomic group in each being Lactobacillus, Lachnospiraceae, Prevotella, and Sneathia. Regarding differences in organism composition between risk behavior groups, the abundance of Atopobium (relative ratio (RR)=0.24; 95%CI 0.11-0.54) and Parvimonas (RR=0.33; 95%CI 0.11-0.93) were significantly lower in WSW than WSM, the abundance of Prevotella was significantly higher in WSW than WSWM (RR=1.77; 95%CI 1.10-2.86), and the abundance of Atopobium (RR=0.41; 95%CI 0.18-0.88) was significantly lower in WSWM than WSM. Overall, WSM had the highest diversity of bacterial taxa.

CONCLUSION

The microbiology of BV among women in different risk behavior groups is heterogeneous. WSM in this study had the highest diversity of bacterial taxa. Additional studies are needed to better understand these differences.

Novel PCR-based methods enhance characterization of vaginal microbiota in a bacterial vaginosis patient before and after treatment

Deep characterization, even by next-generation sequencing, of the vaginal microbiota in healthy women or posttreatment bacterial vaginosis patients is limited by the dominance of lactobacilli. To improve detection, we offer two approaches: quantitative PCR (qPCR) using phylogenetic branch-inclusive primers and sequencing of broad-spectrum amplicons generated with oligomers that block amplification of lactobacilli.

Composition of the vaginal microbiota in women of reproductive age--sensitive and specific molecular diagnosis of bacterial vaginosis is possible?

BACKGROUND AND OBJECTIVE

Bacterial vaginosis (BV) is the most common vaginal disorder, characterized by depletion of the normal lactobacillus-dominant microbiota and overgrowth of commensal anaerobic bacteria. This study aimed to investigate the composition of the vaginal microbiota in women of reproductive age (healthy women and women with BV), with the view of developing molecular criteria for BV diagnosis.

MATERIALS AND METHODS

Vaginal samples from 163 women (79 control, 73 BV and 11 intermediate (Lactobacillary grade II flora) cases) were analyzed using 454 pyrosequencing of the hypervariable regions V3-V4 of the 16S rRNA gene and 16 quantitative bacterial species/genus-specific real-time PCR assays. Sensitivities and specificities of potential BV markers were computed using the Amsel criteria as reference standard for BV. The use of quantitative thresholds for prediction of BV, determined for both relative abundance measured with 454 pyrosequencing and bacterial load measured with qPCR, was evaluated.

RESULTS

Relative to the healthy women, the BV patients had in their vaginal microbiota significantly higher prevalence, loads and relative abundances of the majority of BV associated bacteria. However, only Gardnerella vaginalis, Atopobium vaginae, Eggerthella, Prevotella, BVAB2 and Megasphaera type 1 detected at or above optimal thresholds were highly predictable for BV, with the best diagnostic accuracy shown for A. vaginae. The depletion of Lactobacillus species combined with the presence of either G. vaginalis or A. vaginae at diagnostic levels was a highly accurate BV predictor.

CONCLUSIONS

Quantitative determination of the presence of G. vaginalis, A. vaginae, Eggerthella, Prevotella, BVAB2 and Megasphaera type 1 as well as the depletion of Lactobacillus was highly accurate for BV diagnosis. Measurements of abundance of normal and BV microbiota relative to total bacteria in vaginal fluid may provide more accurate BV diagnosis, and be used for test-of-cure, rather than qualitative detection or absolute counts of BV related microorganisms.

Understanding vaginal microbiome complexity from an ecological perspective

The various microbiota normally associated with the human body have an important influence on human development, physiology, immunity, and nutrition. This is certainly true for the vagina wherein communities of mutualistic bacteria constitute the first line of defense for the host by excluding invasive, nonindigenous organisms that may cause disease. In recent years much has been learned about the bacterial species composition of these communities and how they differ between individuals of different ages and ethnicities. A deeper understanding of their origins and the interrelationships of constituent species is needed to understand how and why they change over time or in response to changes in the host environment. Moreover, there are few unifying theories to explain the ecological dynamics of vaginal ecosystems as they respond to disturbances caused by menses and human activities such as intercourse, douching, and other habits and practices. This fundamental knowledge is needed to diagnose and assess risk to disease. Here we summarize what is known about the species composition, structure, and function of bacterial communities in the human vagina and the applicability of ecological models of community structure and function to understanding the dynamics of this and other ecosystems that comprise the human microbiome.

Efficacy of rifaximin vaginal tablets in treatment of bacterial vaginosis: a molecular characterization of the vaginal microbiota

Bacterial vaginosis (BV) is a common vaginal disorder characterized by an alteration of the vaginal bacterial morphotypes, associated with sexually transmitted infections and adverse pregnancy outcomes. The purpose of the present study was to evaluate the impact of different doses of rifaximin vaginal tablets (100 mg/day for 5 days, 25 mg/day for 5 days, and 100 mg/day for 2 days) on the vaginal microbiota of 102 European patients with BV enrolled in a multicenter, double-blind, randomized, placebo-controlled study. An integrated molecular approach based on quantitative PCR (qPCR) and PCR-denaturing gradient gel electrophoresis (PCR-DGGE) was used to investigate the effects of vaginal tablets containing the antibiotic. An increase in members of the genus Lactobacillus and a decrease in the BV-related bacterial groups after the antibiotic treatment were demonstrated by qPCR. PCR-DGGE profiles confirmed the capability of rifaximin to modulate the composition of the vaginal microbial communities and to reduce their complexity. This molecular analysis supported the clinical observation that rifaximin at 25 mg/day for 5 days represents an effective treatment to be used in future pivotal studies for the treatment of BV.

Development and validation of a semiquantitative, multitarget PCR assay for diagnosis of bacterial vaginosis

Quantitative PCR assays were developed for 4 organisms reported previously to be useful positive indicators for the diagnosis of bacterial vaginosis (BV)--Atopobium vaginae, Bacterial Vaginosis-Associated Bacterium 2 (BVAB-2), Gardnerella vaginalis, and Megasphaera-1--and a single organism (Lactobacillus crispatus) that has been implicated as a negative indicator for BV. Vaginal samples (n = 169), classified as positive (n = 108) or negative (n = 61) for BV based on a combination of the Nugent Gram stain score and Amsel clinical criteria, were analyzed for the presence and quantity of each of the marker organisms, and the results were used to construct a semiquantitative, multiplex PCR assay for BV based on detection of 3 positive indicator organisms (A. vaginae, BVAB-2, and Megasphaera-1) and classification of samples using a combinatorial scoring system. The prototype BV PCR assay was then used to analyze the 169-member developmental sample set and, in a prospective, blinded manner, an additional 227 BV-classified vaginal samples (110 BV-positive samples and 117 BV-negative samples). The BV PCR assay demonstrated a sensitivity of 96.7% (202/209), a specificity of 92.2% (153/166), a positive predictive value of 94.0%, and a negative predictive value of 95.6%, with 21 samples (5.3%) classified as indeterminate for BV. This assay provides a reproducible and objective means of evaluating critical components of the vaginal microflora in women with signs and symptoms of vaginitis and is comparable in diagnostic accuracy to the conventional gold standard for diagnosis of BV.