Chronic endometritis (CE) is an asymptomatic inflammation of the endometrial mucosa, mainly produced by bacterial infection. It is a common pathological finding in infertile patients, causing repeated implantation failure and recurrent pregnancy loss. This blinded study investigated the real-time polymerase chain reaction (RT-PCR) as an objective tool to diagnose CE, overcoming the conflicting diagnoses produced by the classical methods of histology, hysteroscopy and microbial culture. The molecular method was able to quantitatively identify nine bacterial pathogens associated with CE, with a concordance of 77% with all the classic diagnostic methods. Next-generation sequencing also supported these findings. This study demonstrates the potential of molecular microbiology in the accurate diagnosis of CE, thus enabling a targeted therapy. accompanied by widespread decidualized features in the stroma.

The microbiota has emerged as a new factor in normal endometrial function. This review describes the importance of the reproductive tract microbiome in health and disease, and its impact on fertility and pregnancy outcomes. It elucidates the technical details of modern sequencing-based techniques and illustrates their superiority over culture-based techniques when assessing low biomass microbiomes, such as the endometrium. The review describes the physiological dominance of the Lactobacillus species in the reproductive tract and discusses the observed abnormalities in the microbiota in various gynecological conditions such as chronic endometritis, endometriosis and cancer. In addition, the detrimental effects of an altered microbiome in ART and pregnancy outcomes are explored.

This article reports three separate prospective pilot studies characterizing the uterine microbiota by 454 pyrosequencing of the V3-V5 region of the 16S ribosomal RNA gene. First, it showed that vaginal and endometrial microbiota, despite being very similar, present distinct bacterial communities in 20% of asymptomatic reproductive age women. Secondly, the study demonstrated the stability of the endometrial microbiota during the acquisition of endometrial receptivity. Finally, this study showed that dysbiosis of the endometrial microbiota led to poor reproductive outcomes. The endometrial microbiota was classified as Lactobacillus-dominated microbiota (≥90%, LD) or non-Lactobacillus dominated microbiota (<90%, NLD), and the NLD profile was associated with significantly decreased rates of implantation, pregnancy, ongoing pregnancy, and live birth in IVF patients. This is a landmark paper describing the microbiological dimension in infertility and ART.