Vaginal lactobacilli, probiotics, and IVF

Characterization of vaginal Lactobacillus species as a predictor of fertility among Iranian women with unexplained recurrent miscarriage and fertile women without miscarriage history using machine learning modeling

BACKGROUND

Lactobacillus spp. are the predominant bacteria of the vaginal tract, the alteration of which has been previously linked to miscarriage. Here, we investigated differences between selected vaginal Lactobacillus species of women with a history of recurrent miscarriages and fertile women without a history of miscarriage in Iran.

METHODS AND RESULTS

Vaginal swabs were taken from 29 fertile and 24 infertile women and quantitative real-time PCR (qPCR) assay was used to determine a selection of vaginal Lactobacillus species in both groups. The logistic regression (LR) model, Naive Bayes (NB) model, support vector machine model (SVM), and neural network model (NN) were developed to predict disease outcome by selected variables. LR analysis was used to construct a nomogram indicating predictions of the risk of miscarriage. The most abundant species among the patients were L. rhamnosus, L. ruminis, and L. acidophilus, while L. gasseri, L. vaginalis, L. fermentum, and L. iners were more abundant in healthy subjects. The distribution of L. ruminis, L. iners, and L. rhamnosus was higher in patients, while L. acidophilus, L. gasseri, and L. fermentum were highly distributed among healthy subjects. Higher AUC in predicting the disease outcome was observed for L. gasseri, L. rhamnosus, L. fermentum, and L. plantarum.

CONCLUSION

Our findings provide experimental evidence of vaginal Lactobacillus imbalance in infertile women and a suitable predictor for miscarriage based on the AUC algorithms. Further studies with larger sample size and using high-throughput technologies are needed to boost our understanding of the role of lactobacilli in miscarriage.

Pregnancy outcomes after vaginal probiotic supplementation before frozen embryo transfer: a randomized controlled study

In women receiving assisted reproductive treatment, intrauterine lactobacilli dominance has been associated with higher rates of pregnancy achievement. This randomized controlled trial conducted in the fertility clinic of the university hospital from 7 August 2019 to May 2021, aimed to compare the clinical outcome of embryo transfer in frozen-thaw cycles with Lactobacillus supplementation prior to embryo transfer and the standard treatment. A total of 340 infertile women underwent randomization. The biochemical and clinical pregnancy rates were comparable between the groups (39.9 and 34.2% in the study group vs. 41.8 and 31.7% in the control group); however, the miscarriage rate was significantly decreased in the study group (9.5 vs. 19.1%, respectively, p = 0.02), [OR = 0.44, 95% CI (0.23, 0.86)]. Among 49 women diagnosed with bacterial vaginosis, the live birth rate in the study group was higher than the control group (42.31 vs. 26.09%, p = 0.23), [OR = 2.08, 95% CI (0.62, 6.99)]. In the blastocyst transfer group (n = 206), the live birth rate was significantly higher in the study group than in the control group (35.71 vs. 22.22%, p = 0.03) [OR = 1.9, 95% CI (1.05, 3.59)]. Therefore, intravaginal lactobacilli supplementation before embryo transfer in the frozen-thaw cycle did not improve the biochemical and clinical pregnancy rate in the general population but significantly reduced the miscarriage rate.Trial Registration: TCTR20190429001 (29/04/2019) @ www.thaiclinicaltrials.org .

The female reproductive tract microbiotas, inflammation, and gynecological conditions

The intricate interactions between the host cells, bacteria, and immune components that reside in the female reproductive tract (FRT) are essential in maintaining reproductive tract homeostasis. Much of our current knowledge surrounding the FRT microbiota relates to the vaginal microbiota, where ‘health’ has long been associated with low bacterial diversity and Lactobacillus dominance. This concept has recently been challenged as women can have a diverse vaginal microbial composition in the absence of symptomatic disease. The structures of the upper FRT (the endocervix, uterus, Fallopian tubes, and ovaries) have distinct, lower biomass microbiotas than the vagina; however, the existence of permanent microbiotas at these sites is disputed. During homeostasis, a balance exists between the FRT bacteria and the immune system that maintains immune quiescence. Alterations in the bacteria, immune system, or local environment may result in perturbances to the FRT microbiota, defined as dysbiosis. The inflammatory signature of a perturbed or “dysbiotic” FRT microbiota is characterized by elevated concentrations of pro-inflammatory cytokines in cervical and vaginal fluid. It appears that vaginal homeostasis can be disrupted by two different mechanisms: first, a shift toward increased bacterial diversity can trigger vaginal inflammation, and second, local immunity is altered in some manner, which disrupts the microbiota in response to an environmental change. FRT dysbiosis can have negative effects on reproductive health. This review will examine the increasing evidence for the involvement of the FRT microbiotas and inflammation in gynecologic conditions such as endometriosis, infertility, and endometrial and ovarian cancer; however, the precise mechanisms by which bacteria are involved in these conditions remains speculative at present. While only in their infancy, the use of antibiotics and probiotics to therapeutically alter the FRT microbiota is being studied and is discussed herein. Our current understanding of the intimate relationship between immunity and the FRT microbiota is in its early days, and more research is needed to deepen our mechanistic understanding of this relationship and to assess how our present knowledge can be harnessed to assist in diagnosis and treatment of gynecologic conditions.

Microbiome Compositions From Infertile Couples Seeking In Vitro Fertilization, Using 16S rRNA Gene Sequencing Methods: Any Correlation to Clinical Outcomes?

Background

Bacterial infections are usually suspected in infertile couples seeking IVF with no clear understanding of the microbial compositions present in the seminal fluids and vaginal niche of the patients. We used next-generation sequencing technology to correlate microbiota compositions with IVF clinical outcomes.

Methods

Thirty-six couples were recruited to provide seminal fluids and vaginal swabs. Bacterial DNA was extracted, and V4 region of the 16S rRNA was amplified and sequenced in a pair-end configuration on the Illumina MiSeq platform rendering 2 × 150 bp sequences. Microbial taxonomy to species level was generated using the Greengenes database. Linear discriminant analysis (LDA) effect size (LEfSe) was used to identify biologically and statistically significant differences in relative abundance.

Results

Seminal fluid microbiota compositions had lower bacterial concentrations compared with the vagina, but species diversity was significantly higher in seminal fluid samples. Azoospermic subjects had more relative abundance of Mycoplasma and Ureaplasma. In Normospermic semen, Lactobacillus (43.86%) was the most abundant, followed by Gardnerella (25.45%), while the corresponding vaginal samples, Lactobacillus (61.74%) was the most abundant, followed by Prevotella (6.07%) and Gardnerella (5.86%).

Conclusions

Semen samples with positive IVF were significantly colonized by Lactobacillus jensenii (P=0.002), Faecalibacterium (P=0.042) and significantly less colonized by Proteobacteria, Prevotella, Bacteroides, and lower Firmicutes/Bacteroidetes ratio compared with semen samples with negative IVF. Vaginal samples with positive IVF clinical outcome were significantly colonized by Lactobacillus gasseri, less colonized by Bacteroides and Lactobacillus iners. This study has opened a window of possibility for Lactobacillus replenishments in men and women before IVF treatment.

Vaginal Probiotics for Reproductive Health and Related Dysbiosis: Systematic Review and Meta-Analysis

The use of probiotics in reproductive-related dysbiosis is an area of continuous progress due to the growing interest from clinicians and patients suffering from recurrent reproductive microbiota disorders. An imbalance in the natural colonization sites related to reproductive health—vaginal, cervicovaginal, endometrial, and pregnancy-related altered microbiota—could play a decisive role in reproductive outcomes. Oral and vaginal administrations are in continuous discussion regarding the clinical effects pursued, but the oral route is used and studied more often despite the need for further transference to the colonization site. The aim of the present review was to retrieve the standardized protocols of vaginal probiotics commonly used for investigating their microbiota modulation capacities. Most of the studies selected focused on treating bacterial vaginosis (BV) as the most common dysbiosis; a few studies focused on vulvovaginal candidiasis (VVC) and on pretreatment during in vitro fertilization (IVF). Vaginal probiotic doses administered were similar to oral probiotics protocols, ranging from ≥10⁷ CFU/day to 2.5 × 10¹⁰ CFU/day, but were highly variable regarding the treatment duration timing. Moderate vaginal microbiota modulation was achieved; the relative abundance of abnormal microbiota decreased and Lactobacillus species increased.

Muted responses to chronic experimental nitrogen deposition on the Colorado Plateau

Anthropogenic nitrogen (N) deposition is significantly altering both community structure and ecosystem processes in terrestrial ecosystems across the globe. However, our understanding of the consequences of N deposition in dryland systems remains relatively poor, despite evidence that drylands may be particularly vulnerable to increasing N inputs. In this study, we investigated the influence of 7 years of multiple levels of simulated N deposition (0, 2, 5, and 8 kg N ha^-1 year^-1) on plant community structure and biological soil crust (biocrust) cover at three semi-arid grassland sites spanning a soil texture gradient. Biocrusts are a surface community of mosses, lichens, cyanobacteria, and/or algae, and have been shown to be sensitive to N inputs. We hypothesized that N additions would decrease plant diversity, increase abundance of the invasive annual grass Bromus tectorum, and decrease biocrust cover. Contrary to our expectations, we found that N additions did not affect plant diversity or B. tectorum abundance. In partial support of our hypotheses, N additions negatively affected biocrust cover in some years, perhaps driven in part by inter-annual differences in precipitation. Soil inorganic N concentrations showed rapid but ephemeral responses to N additions and plant foliar N concentrations showed no response, indicating that the magnitude of plant and biocrust responses to N fertilization may be buffered by endogenous N cycling. More work is needed to determine N critical load thresholds for plant community and biocrust dynamics in semi-arid systems and the factors that determine the fate of N inputs.

Probiotic therapy in couples with infertility: A systematic review

The reproductive microbiome is becoming increasingly recognised for its influence on fertility. While there has been much work to investigate the treatment of bacterial vaginosis and disordered microbiomes in optimizing outcomes in Assisted Reproductive Technology (ART), the role of routinely prescribed probiotics is yet to be established. The therapeutic potential of probiotic therapy remains an exciting opportunity in ART and this review endeavours to summarise its evidence to date. A systematic review of MEDLINE (Pubmed), Allied Health Literature (CINAHL), EMBASE, Web of Science and the Cochrane database was performed on 7th May 2019, and repeated on 26th August 2019. The search was built using the terms 'subfertility;' 'probiotic therapy;' 'clinical pregnancy rate' and 'assisted reproductive outcomes.' The primary outcome was change in clinical pregnancy rate. Secondary outcomes included improvements in male and female fertility parameters and microbial assessment. The initial search found 882 articles, of which 26 full manuscripts were reviewed. Four articles were eligible for inclusion. Of the two studies that reported the primary outcome, only one study found probiotics increased the clinical pregnancy rate non-significantly (48.0%-58.8%, p = 0.47). It also found higher miscarriage rate (30 % vs 16.6 %, p = 0.47) in the group treated with probiotics. Both studies on males with oral probiotic found significantly improved sperm motility. While benefit in sperm motility has been observed with male probiotic therapy, there is conflicting evidence on the efficacy of probiotic therapy for women undergoing assisted reproduction. High quality randomized studies are needed to definitively examine probiotic therapy and establish its benefit for couples undergoing assisted reproduction.

Uterine microbiome-low biomass and high expectations†

The existence of different bacterial communities throughout the female reproductive tract has challenged the traditional view of human fetal development as a sterile event. There is still no consensus on what physiological microbiota exists in the upper reproductive tract of the vast majority of women who are not in periods of infection or pregnancy, and the role of bacteria that colonize the upper reproductive tract in uterine diseases or pregnancy outcomes is not well established. Despite published studies and advances in uterine microbiome sequencing, some study aspects-such as study design, sampling method, DNA extraction, sequencing methods, downstream analysis, and assignment of taxa-have not yet been improved and standardized. It is time to further investigate the uterine microbiome to increase our understanding of the female reproductive tract and to develop more personalized reproductive therapies, highlighting the potential importance of using microbiological assessment in infertile patients.

Taxonomical and Functional Assessment of the Endometrial Microbiota in A Context of Recurrent Reproductive Failure: A Case Report

Investigation of the microbial community in the female reproductive tract has revealed that the replacement of a community dominated by Lactobacillus with pathogenic bacteria may be associated with implantation failure or early spontaneous abortion in patients undergoing assisted reproductive technology (ART) treatment. Herein we describe taxonomically and functionally the endometrial microbiome of an infertile patient with repeated reproductive failures (involving an ectopic pregnancy and two clinical miscarriages). The microbiological follow-up is presented over 18-month in which the microbiota was evaluated in six endometrial fluid samples. The microbial profile of 16S rRNA gene sequencing showed a persistent infection with Gardnerella and other bacterial taxa such as Atopobium and Bifidobacterium. In addition, taxonomic and functional analysis by whole metagenome sequencing in the endometrial fluid sample collected before one clinical miscarriage suggested the presence of multiple Gardnerella vaginalis clades with a greater abundance of clade 4, usually associated with metronidazole resistance. These results revealed a persistent G. vaginalis endometrial colonization presenting genetic features consistent with antimicrobial resistance, biofilm formation, and other virulence factors, which could be related to the reproductive failure observed.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.

The primate vaginal microbiome: comparative context and implications for human health and disease

The primate body hosts trillions of microbes. Interactions between primate hosts and these microbes profoundly affect primate physiology, reproduction, health, survival, and ultimately, evolution. It is increasingly clear that primate health cannot be understood fully without knowledge of host-microbial interactions. Our goals here are to review what is known about microbiomes of the female reproductive tract and to explore several factors that influence variation within individuals, as well as within and between primate species. Much of our knowledge of microbial variation derives from studies of humans, and from microbes located in nonreproductive regions (e.g., the gut). We review work suggesting that the vaginal microbiota affects female health, fecundity, and pregnancy outcomes, demonstrating the selective potential for these agents. We explore the factors that correlate with microbial variation within species. Initial colonization by microbes depends on the manner of birth; most microbial variation is structured by estrogen levels that change with age (i.e., at puberty and menopause) and through the menstrual cycle. Microbial communities vary by location within the vagina and can depend on the sampling methods used (e.g., swab, lavage, or pap smear). Interindividual differences also exist, and while this variation is not completely understood, evidence points more to differences in estrogen levels, rather than differences in external physical environment. When comparing across species, reproductive-age humans show distinct microbial communities, generally dominated by Lactobacillus, unlike other primates. We develop evolutionary hypotheses to explain the marked differences in microbial communities. While much remains to be done to test these hypotheses, we argue that the ample variation in primate mating and reproductive behavior offers excellent opportunities to evaluate host-microbe coevolution and adaptation.

OPINION PAPER: Quo vadis – EFSA?

In times when human life and quality of life remain threatened by infectious diseases, increasing microbial resistance and a diminished armamentarium of treatments, you might think that the European Commission would urgently seek and encourage alternative approaches. On the contrary, the European Food Safety Authority (EFSA) has created a panel that has ignored good science, over-ridden peer-reviewed medical studies, and seems intent on breaking the back of a validated approach to infectious disease management, namely probiotics. The recent rejection of a simple and quite bland claim related to vaginal health emphasises the travesty of this bureaucracy. Herein, the science fights back and counters the critique of EFSA.

Probiotics for the treatment of bacterial vaginosis

BACKGROUND

The dominance of lactobacilli in healthy vaginal microbiota and its depletion in bacterial vaginosis (BV) has given rise to the concept of oral or vaginal instillation of probiotic Lactobacillus strains for the management of this condition.

OBJECTIVES

To ascertain the efficacy of probiotics in the treatment of BV.

SEARCH STRATEGY

We searched electronic databases irrespective of publication status or language. These included: Cochrane Central Register of Controlled Trials (CENTRAL), the HIV/AIDS and STD Cochrane Review Groups' specialized registers, the Cochrane Complementary Medicine Field's Register of Controlled Trials, MEDLINE (1966 to 2008), EMBASE (1980 to 2007), ISI science citation index (1955 to 2007), CINAHL (Cumulative Index to Nursing & Allied Health Literature (1982 to 2007).We handsearched of specialty journals, conference proceedings and publications list on the website of the International Scientific Association of Probiotics and Prebiotics (http://www.isapp.net/default.asp).For unpublished studies or ongoing trials, we contacted authors from relevant publications, nutraceutical companies and probiotic-related scientific associations. We searched electronic databases on ongoing clinical trials.

SELECTION CRITERIA

Randomized controlled trials using probiotics for the treatment of women of any age diagnosed with bacterial vaginosis, regardless of diagnostic method used. The probiotic preparation could be single or "cocktail" of strains, any preparation type/dosage/route of administration. Studies comparing probiotics with placebo, probiotics used in conjunction with conventional antibiotics compared with placebo or probiotics alone compared with conventional antibiotics were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

We screened titles and abstracts , obtained full reports of relevant trialsand independently appraised them for eligibility. A data extraction form was used to extract data from the four included studies. For dichotomous outcomes, odds ratios (OR) and 95% confidence intervals (CI) were derived for each study using RevMan (versions 4.2 and 5). We did not perform meta-analysis due to significant differences in the probiotic preparations and trial methodologies.

MAIN RESULTS

Analysis suggests beneficial outcome of microbiological cure with the oral metronidazole/probiotic regimen (OR 0.09 (95% CI 0.03 to 0.26)) and the probiotic/estriol preparation (OR 0.02, (95% CI 0.00 to 0.47)). For the probiotic/estriol preparation, the OR and 95% CI for physician-reported resolution of symptoms was OR 0.04 (95% CI 0.00 to 0.56).

AUTHORS' CONCLUSIONS

The results do not provide sufficient evidence for or against recommending probiotics for the treatment of BV. The metronidazole/probiotic regimen and probiotic/estriol perparation appear promising but well-designed randomized controlled trials with standardized methodologies and larger patient size are needed.

Changes in the predominant human Lactobacillus flora during in vitro fertilisation

Background

Signature matching of nucleotide sequences in the V1 and V3 regions 16S rRNA genes using pyrosequencing technology is a powerful tool for typing vaginal Lactobacilli to the species level and has been used for investigating the vaginal microbial niche.

Methods

This study has characterized the normal cultivable vaginal Lactobacillus flora at varying estradiol levels in plasma; the study comprised 17 patients undergoing ovarian stimulation for In Vitro Fertilization (IVF) treatment. The vaginal status of each participant was initially assessed as normal according to Amsel and Nugent criteria.

Results

L. crispatus, L. gasseri and/or L. jensenii were present in 10 of the patients throughout the study period, and little variation among these three species was encountered in individual patients. The flora of three women was dominated by L. delbrüeckii, L. rhamnosus or L. vaginalis. One woman exhibited a dominance of L. iners. The flora of the remaining three women were initially dominated by L. rhamnosus or L. reuteri, but as their estrogen levels rose, their flora composition altered, to become dominated by one of the three species most common in a normal, healthy vagina.

Conclusion

Signature matching of nucleotide sequences in the V1 and V3 regions of 16S rRNA genes is a discriminative tool for the study of vaginal Lactobacilli and can be used to track the Lactobacillus flora under a variety of physiological conditions.