Colonisation bactérienne vaginale anormale et implantation en assistance médicale à la procréation

Role of vulvovaginal candidiasis infection in infertility: systematic review and meta-analysis

OBJECTIVE

To evaluate the relationship between fungal infection in the female genital tract and infertility.

DATA SOURCES

A systematic review was carried out, and the search was conducted in Medline, Embase, Web of Science, Google Scholar, and Cochrane Library databases until August 2022. The search strategy used standardized keywords such as "candidiasis" and "infertility," combined with their respective synonyms. The search was limited to human studies, with no language restrictions.

STUDY ELIGIBILITY CRITERIA

Primary articles that evaluated women of reproductive age with and without infertility and related to the presence or absence of candidiasis were included.

STUDY APPRAISAL AND SYNTHESIS METHODS

For the analyses, the odds ratio association measure was used with a confidence interval of 95% using RevMan software (version 5.4).

RESULTS

Eight studies, published between 1995 and 2021 in different countries around the world, were included in this systematic review. Two studies were excluded after sensitivity analysis. A total of 909 participants were included in the group of infertile women and 2363 women in the control group. The age of the evaluated women varied between 18 and 50 years. The random effect model was used and showed no significant difference when comparing candidiasis between fertile and infertile women (odds ratio: 1.44; 95% confidence interval 0.86, 2.41 p= 0.17).

CONCLUSIONS

There was no association between candidiasis and female sterility.

Male infertility and the human microbiome

The historical belief in urology was that the genitourinary system should be sterile in a normal, healthy, asymptomatic adult. This idea was perpetuated for decades until research revealed a diverse microbiota existing in human anatomical niches that contributed to both human health and disease processes. In recent years, the search for an etiology and modifiable risk factors in infertility has turned to the human microbiome as well. Changes in the human gut microbiome have been associated with changes in systemic sex hormones and spermatogenesis. Certain microbial species are associated with higher levels of oxidative stress, which may contribute to an environment higher in oxidative reactive potential. Studies have demonstrated a link between increased oxidative reactive potential and abnormal semen parameters in infertile men. It has also been hypothesized that antioxidant probiotics may be able to correct an imbalance in the oxidative environment and improve male fertility, with promising results in small studies. Further, the sexual partner's microbiome may play a role as well; studies have demonstrated an overlap in the genitourinary microbiomes in sexually active couples that become more similar after intercourse. While the potential applications of the microbiome to male fertility is exciting, there is a need for larger studies with uniform microbial sequencing procedures to further expand this topic.

Semen dysbiosis—just a male problem?

Seminal microflora is crucial to male fertility. Dysbiosis—disturbance of quantitative ratios of individual bacteria or appearance of pathogenic species—rarely results in symptomatic disease. Inflammation results in decreased sperm production, lower motility, or morphological changes and, in the long term, can cause ejaculatory duct obstruction, leading to infertility. Moreover, it may cause infection of the partner’s female genital tract. Dysbiosis in both partners results in fertility problems, disorders in embryo implantation, or miscarriages. In addition, chronic inflammation of the male genitourinary system may accelerate the appearance of antisperm antibodies. A comprehensive examination of seminal microflora can clarify the causes of infertility or prevent pathological conditions that affect seminal parameters. Seminal microflora as a direct impact on fertility problems as well as a decrease in the effectiveness of assisted reproduction methods, insemination, or in vitro procedures.

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.

The effect of endocervical and catheter bacterial colonisation during in vitro fertilisation and embryo transfer (IVF-ET) on IVF success rate among asymptomatic women: a longitudinal prospective study

The adverse effects of bacterial contamination during in vitro fertilisation and embryo transfer (IVF-ET) have been studied previously. However, data on asymptomatic women with positive bacterial culture and their IVF outcome are lacking. This prospective longitudinal study was conducted on 74 women undergoing IVF-ET, of whom specimens from the endocervix and ET catheter were taken and sent to a laboratory for microbiological assessment. Then, patients were followed up for evaluation of chemical pregnancy (β-HCG > 25 mIU/mL) and clinical pregnancy (detected foetal heartbeat). The findings revealed that there was no significant difference in terms of biochemical (35.4% vs. 19.2%, p= .116) and clinical pregnancy rate (25.0% vs. 15.4%, p= .257) among ET catheter culture positive and negative women. This finding allows us to conclude that the positive culture in the absence of clinical signs of infection may not increase the risk of implantation failure.Impact StatementWhat is already known on this subject? There is growing evidence indicating that endometritis may decrease the endometrial receptiveness in in vitro fertilisation (IVF) cycles; however, there is a paucity of knowledge regarding IVF outcomes when the bacterial culture of embryo transfer (ET) catheter is positive.What the results of this study add? The present study demonstrates that positive ET catheter culture in asymptomatic women does not increase the risk of IVF failure.What the implications are of these findings for clinical practice and/or further research? Positive-culture, per se, may not be associated with poor IVF outcomes and further studies should be undertaken on this topic in various clinical settings using different protocols.

Microbiota and Human Reproduction: The Case of Male Infertility

The increasing interest in metagenomics is enhancing our knowledge regarding the composition and role of the microbiota in human physiology and pathology. Indeed, microbes have been reported to play a role in several diseases, including infertility. In particular, the male seminal microbiota has been suggested as an important factor able to influence couple's health and pregnancy outcomes, as well as offspring health. Nevertheless, few studies have been carried out to date to deeper investigate semen microbiome origins and functions, and its correlations with the partner's reproductive tract microbiome. Here, we report the state of the art regarding the male reproductive system microbiome and its alterations in infertility.

Does bacterial colonization during embryo transfer have an impact on pregnancy rate in ICSI? : Tunisian preliminary results

INTRODUCTION

Embryos' transfer into the uterine cavity remains a limiting factor in the success of intracytoplasmic sperm injection (ICSI). This study aimed to evaluate the impact of cervico-vaginal colonization on ICSI outcomes.

MATERIEL AND METHODS

Longitudinal, prospective and analytical study, conducted from February 1 st to October 31 st, 2017. On the day of embryos' transfer, patients with the following criteria were included: Age ≤ 40, normal uterine ultrasound and hysteroscopy, first or second attempt of ICSI, use of fresh semen and transfer of at least one good quality embryo. Three samples were done for microbiological analysis: vaginal secretions, cervical mucus and the tip of the transfer catheter.

RESULTS

The study included 40 patients. Pregnancy rate was 52.5 %. Catheter contamination occurred in nine cases (22.5 %). The most frequently isolated bacteria were Streptococcus anginosus (37 % of cases), Gardnerella vaginalis (27 % of cases) and Streptococcus agalactiae (18 % of cases). In all cases of contamination, the same bacteria were found also in the vagina and cervical mucus. In cases of contamination with Gardnerella vaginalis, the study of vaginal flora showed bacterial vaginosis. No pregnancy was obtained when contamination of the transfer catheter occurred. In the absence of contamination, pregnancy rate was 61.2 % (ρ = 0.003). Both populations (patients with catheter contamination and patients without catheter contamination) were comparable regarding epidemiological characteristics and ICSI attempt data.

CONCLUSION

Contamination of the transfer catheter by cervical-vaginal bacteria appears to affect IVF results. Systematic antibiotic prophylaxis could be proposed to reduce this negative impact.

Differential Composition of Vaginal Microbiome, but Not of Seminal Microbiome, Is Associated With Successful Intrauterine Insemination in Couples With Idiopathic Infertility: A Prospective Observational Study

Background

Vaginal and seminal microbiomes have gained increasing interest for their involvement in reproductive health and fertility. However, their role in reproductive outcome is not fully understood yet. In this study, we aimed to correlate the vaginal and the seminal microbiome of 23 couples with idiopathic infertility to the clinical pregnancy rate after intrauterine insemination (IUI).

Methods

Vaginal swabs and seminal fluids were collected on the day of IUI procedure and analyzed through polymerase chain reaction amplification of variable regions 3 and 4 (V3–V4) of 16S ribosomal ribonucleic acid genes and Illumina MiSeq sequencing. The taxonomic data were then correlated to IUI success.

Results

Idiopathic infertile women showed a different average composition of vaginal microbiome compared with control sequences, whereas for seminal counterpart no relevant differences were observed. Furthermore, among idiopathic infertile women, different patterns of Lactobacillus species dominations were observed, with a predominance either of Lactobacillus crispatus, a marker of a healthy vaginal ecosystem, or of Lactobacillus iners and Lactobacillus gasseri, associated with a more dysbiosis-prone environment. More important, considering all investigated variables, vaginal L crispatus domination was the only factor strongly associated to IUI success (P = .0002).

Conclusions

Our results strengthen the potential role of L crispatus in promoting a favorable environment for pregnancy and suggest that microbiome characterization could be useful, together with standard clinical and laboratory assessments, in the pre-IUI evaluation of infertile couples.

The seminal microbiome in health and disease

Owing to the fact that there are more microbial than human cells in our body and that humans contain more microbial than human genes, the microbiome has huge potential to influence human physiology, both in health and in disease. The use of next-generation sequencing technologies has helped to elucidate functional, quantitative and mechanistic aspects of the complex microorganism-host interactions that underlie human physiology and pathophysiology. The microbiome of semen is a field of increasing scientific interest, although this microbial niche is currently understudied compared with other areas of microbiome research. However, emerging evidence is beginning to indicate that the seminal microbiome has important implications for the reproductive health of men, the health of the couple and even the health of offspring, owing to transfer of microorganisms to the partner and offspring. As this field expands, further carefully designed and well-powered studies are required to unravel the true nature and role of the seminal microbiome.

Patients with cervical Ureaplasma Urealyticum and Chlamydia Trachomatis infection undergoing IVF/ICSI-ET: The need for new paradigm

Genital tract infections with ureaplasma urealyticum (UU) and chlamydia trachomatis (CT) are the most frequent sexually-transmitted disease worldwide. UU and CT infections are considered to be the leading cause for infertility and adverse pregnancy outcomes. However, little is known about the specific effect of cervical UU and CT infections on the etiology of female infertility, as well as the pregnancy outcomes of the patients undergoing in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET). In order to find the association between cervical UU and/or CT infection and pregnancy outcomes, we conducted a retrospective case-control study on the patients undergoing IVF/ICSI-ET with cervical UU and/or CT infection. A total of 2208 patients who received IVF/ICSI-ET were enrolled in this study. Data on the general conditions, pregnancy history and clinical pregnant outcomes were analyzed in terms of the cervical UU and CT detection. Our results revealed that cervical UU and CT infections were the risk factors for ectopic pregnancy and tubal factor-induced infertility. Moreover, the pregnancy rate, abortion rate, ectopic pregnancy rate and premature birth rate in patients with UU and/or CT infections showed no significant difference when compared with the control group. We recommend that cervical UU and CT detection should be an optional item for infertility patients and clinical UU detection should differentiate the subtypes of cervical UU. Positive cervical UU and CT infections should not be taken as strict contraindications for IVF/ICSI-ET.

Transfer of IVF-contaminated blastocysts with removal of the zona pellucida resulted in live births

PURPOSE

Bacterial contamination may cause loss or damage to cultured oocytes or embryos, resulting in cancelation or delaying of a fresh embryo transfer. While live births have been reported following the transfer of embryos contaminated with yeast, very little information is available on how to handle embryos with bacterial contamination. We report two cases of successful pregnancy in patients with bacterial contamination of embryo culture dishes.

METHODS

We retrospectively reviewed 878 oocyte retrievals performed between January 2011 and December 2014. Bacterial contamination was recorded in two split IVF/ICSI cases, where contamination occurred in embryo culture drops containing embryos from conventional insemination but not from ICSI on day 3.

RESULTS

To minimize the adverse effects of bacterial contamination on transfer outcomes, we removed the zona pellucida of contaminated frozen blastocysts and successfully obtained clinical pregnancies following transfer of zona-free blastocysts that were previously contaminated during IVF culture.

CONCLUSIONS

Removal of the zona pellucida is an appropriate approach to handle blastocysts contaminated with bacteria during in vitro culture.

Does screening for vaginal infection have an impact on pregnancy rates in intracytoplasmic sperm injection cycles?

Objective:

Assisted reproduction techniques have become widespread worldwide. Considering their costs, physicians endeavor to improve pregnancy rates. Infections are one of the disrupting problems in this arena. We aimed to investigate the effects of screening for vaginal infection on pregnancy rates in intracytoplasmic sperm injection cycles.

Materials and Methods:

One hundred twenty patients randomized into two groups for this study. Patients were screened for vaginal infections in group 1, and no screening was performed in group 2. The assisted reproduction outcomes were investigated and compared between the two groups.

Results:

There was no significant difference between ages, or durations and causes of infertility of patients who conceived and of those who did conceive. Forty-five patients in group 1, and 40 patients in group 2 reached the embryo transfer stage. The rates of conception were 23.5% (n=4) in culture-positive patients (n=17), and 42.9% (n=12) in culture-negative patients (n=28) in group 1. There was no significant difference among patients who were not screened, screen-positive, and screen-negative, in terms of pregnancy rates. None of the patients had Neisseria gonorrhoeae or Trichomonas vaginalis. Bacterial vaginosis was detected in 13 patients, and both bacterial vaginosis and Chlamydia trachomatis were detected in 4 patients. Three of 4 patients who conceived screen-positive and 8 of 12 patients who conceived screen-negative delivered healthily at term.

Conclusion:

No significant difference was found between patients who were sampled for culture and patients who were not sampled in terms of pregnancy rates. Also, no difference was found between the patients who were culture-negative and patients who were treated with antimicrobials after a culture positive result. Further larger studies are warranted to clarify this issue.

Influence of sexual intercourse on genital tract microbiota in infertile couples

Several studies have suggested the association of disturbed genital tract microbiota with infertility. Our aim was to clarify the influence of sexual intercourse on partner's genital tract microbiota in infertile couples. Seventeen couples were studied, and in 5 men inflammatory prostatitis (IP) was diagnosed. Semen samples were collected during menstruation of the female counterpart, two self-collected vaginal samples were taken 3-5 days later - before intercourse and 8-12 h after intercourse. Ureaplasma parvum was found in 59% of women, its prevalence was higher in women whose partner had IP, as well as in half of their male partners. Sexual intercourse caused significant shifts in vaginal microbiota - increase of Nugent score and shifts in cultured microbiota (emergence and disappearance of several species). These changes were less expressed in the presence of normal vaginal microbiota but more prominent in the partners of IP men. These changes may interfere with fertilization.

Fulminant Sepsis after Second-Trimester Amniocentesis in Pregnant Women by in vitro Fertilization and Embryo Transfer

Second-trimester amniocentesis is a common procedure for prenatal diagnosis. Sepsis is a rare complication after amniocentesis and may rapidly deteriorate if prompt treatment, including broad-spectrum antibiotics and removal of the infected abortus, is delayed. In vitro fertilization and embryo transfer (IVF-ET) is a standard final treatment for infertile women. Transvaginal oocyte retrieval is necessary for such women; this procedure potentially causes Escherichia coli attaching and effacing in the abdominal cavity. Here we report that two pregnant women by IVF-ET developed sepsis after second-trimester amniocentesis. The cause of sepsis after amniocentesis is still unknown. We provided the possibility of the causation of the E. coli infection associated with the previous intra-abdominal procedure, but it needs more evidence to prove it.

Embryo transfer: factors involved in optimizing the success

PURPOSE OF REVIEW

Embryo transfer is arguably the most critical step in assisted reproduction. The purpose of this article is to review the different aspects of the procedure in the light of recent evidence.

RECENT FINDINGS

Randomized trials have shown that significantly higher pregnancy rates are obtained when embryo transfer is performed under ultrasound guidance, the embryos are deposited in the middle part of the uterine cavity, an atraumatic technique is used and when low-dose aspirin is routinely administered following the procedure. Blood in the catheter and leaving the embryos inside it for more than 120 s diminish the pregnancy rate significantly. Air in the catheter, immediate removal of the catheter, performing two transfers in the same cycle, prolonged bed rest, sexual intercourse after embryo transfer or the use of sildenafil do not affect the results. Based on currently available evidence, Cochrane reviews have concluded that the live birth rate is not increased by delaying embryo transfer from day two to three or to the blastocyst stage, and that single embryo transfer leads to lower live birth rates than the transfer of two embryos. The value of a mock transfer a few days before the actual procedure has been challenged as the position of the uterus may change. The effect of holding the cervix with a volsellum, routinely administering antibiotics and the superiority of one catheter over the others is still to be determined.

SUMMARY

Recent studies confirm the importance of the various aspects of embryo transfer. More randomized studies are needed to further evaluate them.