Analysis of endometrial microbiota by 16S ribosomal RNA gene sequencing among infertile patients: a single‐center pilot study

Abstract

PurposeThe present study aimed to analyze the endometrial and vaginal microbiome among a Japanese infertile population by sequencing and the impact of the endometrial and vaginal environment on implantation.MethodsIn total, 102 infertile (79 in vitro fertilization [IVF] and 23 non‐IVF) patients and seven healthy volunteers were recruited from August to December, 2017. Endometrial fluid and vaginal discharge samples for sequencing were collected by using an intrauterine insemination catheter. The bacterial status of the endometrium and vagina were analyzed.ResultsThe Lactobacillus‐dominated microbiota (>90% Lactobacillus spp.) in the endometrium vs vagina was 38% (30/79) vs 44.3% (44/79) in the IVF patients, 73.9% (17/23) vs 73.9% (17/23) in the non‐IVF patients, and 85.7% (6/7) vs 85.7% (6/7) in the healthy volunteers. The percentage of endometrial Lactobacillus in the healthy volunteers was highly stable within the same menstrual cycle and even in the following cycle. The major taxonomies were Gardnerella, Streptococcus, Atopobium, Bifidobacterium, Sneathia, Prevotella, and Staphylococcus. Fifteen patients achieved pregnancy by a single vitrified‐warmed blastocyst transfer during this study; the median percentage of Lactobacillus in the pregnant women was 96.45 ± 33.61%.ConclusionA considerable percentage of non‐Lactobacillus‐dominated (NLD) microbiota was found in the endometrium of Japanese infertile women. Increasing the endometrial level of the Lactobacilli to >90% might favor the implantation outcome of NLD infertile patients.

A pilot study and case reports on endometrial microbiota and pregnancy outcome: An analysis using 16S rRNA gene sequencing among IVF patients, and trial therapeutic intervention for dysbiotic endometrium

“…There are limitations of this present study: short follow‐up period, limited study numbers, and not analyzing other aspects of gynecological histories such as sexual contact, past oral contraceptive usage, past antibiotic usage, miscarriage, endometriosis, and bacterial vaginosis. In terms of sample collection, EF specimens may have contained some endocervical fluid, which was distinguished in a previous study, but the endometrial microbiota was not suspected to be carried over from the vaginal microbiota …”

“…The EF specimens were collected either in follicular phase, ovulation phase, or luteal phase of the menstrual cycles, as there was intercyclic stability of the endometrial microbiome in our previous study . There was no statistical difference in the timing of sampling between LDM and NLDM (Table ).…”

“…The reason for this may be simply due to patient recruitment, or there may have been more patients hoping for a second child in the NLDM group, suggesting that childbirth, either by vaginal delivery or cesarean section, may interfere with maternal endometrial microbiota. Other factors that may interfere with endometrial microbiota may be derived from IVF procedures or backgrounds of IVF patients such as infertility period, seminal factor, frequent exposure to gynecological examinations/interventions such as transvaginal examination, uterine catheterization such as IUI or hysterosalpingography, oocyte retrieval, embryo transfer, frequent administration of antibiotics, hormonal fluctuation due to controlled ovarian stimulation, etc . Also, lifestyle habits including sexual activities and sanitary conditions may have an impact on endometrial microbiome, but these were not analyzed in this study.…”

“…Samples from the endometrium were taken from the participants as described previously . Briefly, after cleaning the mucous around the cervical os and the uterine cervix, endometrial fluid (EF) specimens were carefully aspirated with a Kitazato IUI catheter (Kitazato Corporation, Japan) with utmost care not to touch the vaginal wall.…”

“…We have started our study on uterine microbiota by sequencing from August 2017 and found that the percentage of endometrial Lactobacilli in IVF patients was significantly lower than that of non‐IVF patients and healthy volunteers . Also, the median percentages of endometrial Lactobacilli in the pregnant cases were more than 90%, which may implicate the possibility that Lactobacillus dominancy in the human endometrium might benefit embryo implantation . To what extent the human uterine microbiomes are involved in implantation failure is still not clear, and the treatment strategy for dysbiotic endometrium is still not established.…”