Microbiology: The microbiome of the female reproductive tract

Distinct microbial communities exist along the reproductive tract of women, from vagina to fallopian tubes, reports an article published in Nature Communications. These findings challenge the traditional view of human fetal development taking place in a sterile environment. The study also shows that variations in these microbial communities correlate with some uterine-related disorders, potentially serving as biomarkers for certain diseases.

The vagina is known to be home for many microorganisms, but the presence of a defined microbiota in the upper reproductive tract of women, in the absence of infection, has been unclear. Huijue Jia and colleagues analysed microorganisms along the reproductive tract of 110 Chinese women of reproductive age. They collected samples from six sites: lower third of vagina, posterior fornix, cervical canal mucus, endometrium, fallopian tubes, and peritoneal fluid from Douglas’ pouch.

Consistent with previous reports, the authors found that Lactobacillus bacteria dominate the lower tract (vagina, fornix). Lactobacilli progressively become less abundant in the upper tract and are replaced with other types of bacteria, such as Pseudomonas. The authors were able to cultivate bacteria sampled from the upper tract, demonstrating that live bacteria are present in these sites. Finally, the researchers found correlations between variations in the microbiota and the phase of the menstrual cycle, as well as disorders such as hysteromyoma, adenomyosis and infertility due to endometrosis.

The findings support the idea that live bacteria exist in the female upper reproductive tract. They also indicate that it might be possible to survey the health status of the uterus and peritoneal cavity by analysing the microbiota of the cervical mucosa. Further research, using larger and prospective cohorts, would be needed to validate the potential use of cervical microbiota analysis as biomarker of vagino-uterine disorders.