Lactobacillus crispatus-dominated vaginal microbiome and Acinetobacter-dominated seminal microbiome support beneficial ART outcome

Abstract

Introduction: Despite the considerable progress made in assisted reproductive technologies (ART), the implantation rate of transferred embryos remains low and in many cases, the reasons for failure remain unclear. We aimed to determine the potential impact of female and male partners' reproductive tract microbiome composition on ART outcome.

Material and methods: The ART couples (n = 97) and healthy couples (n = 12) were recruited into the study. The smaller healthy group underwent a careful selection according to their reproductive and general health criteria. Both vaginal and semen samples were subjected to 16S rDNA sequencing to reveal the bacterial diversity and identify distinct microbial community types. Ethics statement The study was approved by the Ethics Review Committee on Human Research of Tartu University, Tartu, Estonia (protocol no. 193/T-16) on 31 May 2010. Participation in the research was voluntary. Written informed consent was obtained from all study participants.

Results: The men with Acinetobacter-associated community who had children in the past, had the highest ART success rate (P < 0.05). The women with bacterial vaginosis vaginal microbiome community and with L. iners-predominant and L. gasseri-predominant microbiome had a lower ART success rate than women with the L. crispatus-predominant or the mixed lactic-acid-bacteria-predominant type (P < 0.05). The 15 couples where both partners had beneficial microbiome types had a superior ART success rate of 53%, when compared with the rest of the couples (25%; P = 0.023).

Conclusions: Microbiome disturbances in the genital tract of both partners tend to be associated with couple's infertility as well as lower ART success levels and may thus need attention before the ART procedure. The incorporation of genitourinary microbial screening as a part of the diagnostic evaluation process may become routine for ART patients if our results are confirmed by other studies.

Keywords: assisted reproductive technologies (ART); couple; infertility; microbiome; reproductive tract; semen.

FIGURE 1

Boxplot of sample groups with different alpha diversity indices. Asterisks indicate differences between the groups (P < 0.05). H, healthy; I, infertile; ♀, woman; ♂, man.

FIGURE 2

Predominant phyla (A) and families (B) in vaginal and semen samples. Asterisks indicate differences in comparison with healthy controls (P < 0.05). H, healthy; I, infertile; ♀, woman; ♂, man.

FIGURE 3

Hierarchical clustering of vaginal samples. Columns represent female vaginal microbiome and rows represent identified bacterial clusters. A: Nugent score; B: health status and ART result; C: microbiome community type. ART, assisted reproductive technologies; IVF, in vitro fertilization.

FIGURE 4

Hierarchical clustering of semen samples. Columns represent semen microbiome and rows represent identified bacterial clusters. A: WBC concentration in semen, B: health status and ART result, C: microbiome community type. Two samples did not cluster into the groups – in one of them, Veillonella predominated and in another, Haemophilus parainfluenzae predominated. ART, assisted reproductive technologies; IVF, in vitro fertilization.

FIGURE 5

Previous pregnancy loss, body mass index (BMI), primary or secondary infertility, and reproductive tract microbial community types (eight panels) in infertile women undergoing an ART procedure. The figure matrix (NMDS1 vs NMDS2) displays the OTU composition of the individual women on two‐dimensional plane, each woman being presented as an individual datapoint. Women experiencing primary (symbols in green) or secondary (symbols in orange) infertility according to previous pregnancy loss (circle – no previous pregnancy loss; triangle – no data; square – previous pregnancy loss) and their BMI (the bigger the symbol, the heavier the woman). BMI categories: 0, no data; 1, <18.5 kg/m² (underweight); 2, 18.5–24.9 kg/m² (normal weight); 3, 25–29.9 kg/m² (overweight); 4, ≥30 (class I & II obesity). PERMANOVA analysis revealed several associations: microbial community type was significantly associated with women's previous pregnancy loss status (Pr[>F] 0.0417) and primary infertility type was significantly associated with elevated BMI (Pr[>F] 0.0201). ART, assisted reproductive technologies; BMI, body mass index; OTU, operational taxonomic unit.

FIGURE 6

Body mass index (BMI), primary or secondary infertility, fertilization type (IVF vs ICSI), and reproductive tract microbial community types (eight panels) in infertile women undergoing an ART procedure. The figure matrix (NMDSI1 vs NMDS2) displays the OTU composition of the individual women on a two‐dimensional plane, each woman being presented as an individual datapoint. Women experiencing primary (symbols in green) or secondary (symbols in orange) infertility according to the type of fertilization (circle – ICSI; triangle – IVF) and BMI (the bigger the symbol, the heavier the woman). BMI categories: 0, no data; 1, <18.5 kg/m² (underweight); 2, 18.5–24.9 kg/m² (normal weight); 3, 25–29.9 kg/m² (overweight); 4, ≥30 (class I & II obesity). PERMANOVA analysis revealed several associations: fertilization type was significantly associated with women's BMI (Pr[>F] 0.0228; women undergoing ICSI had higher BMI) and microbial community type (Pr[>F] 0.0332). ART, assisted reproductive technologies; BMI, body mass index; ICSI, intracytoplasmic sperm injection; IVF, in vitro fertilization; OTU, operational taxonomic unit.