Endometriosis and Fusobacterium

A new bacterial infection study has connected endometriosis and fusobacterium, as 64% of women with endometriosis are infected with fusobacterium bacteria.

Uterus with Endometriosis

New Study Connects Endometriosis and Fusobacterium

Endometriosis is a very complex condition characterized by the growth of tissues similar to the lining of the womb (endometrium) in unusual places (think your GI tract, fallopian tubes, etc.) [1]. It affects 1 in 10 women.

There’s no simple way to describe endometriosis, mainly due to the severe lack of research into the condition. We still don’t know what causes it. However, it could be related to the human microbiome, according to this year’s study on Fusobacterium.

What Does the New Study on Endometriosis and Fusobacterium Say?

The study proposes a link between women whose endometriums are infected by the Fusobacterium microbe and the mechanism for endometriosis development.

The researchers suggest that endometriosis lesions are promoted by Fusobacterium, which activates an immune response that supports endometrial tissue growth in other organs.

A key finding was higher numbers of a type of cell called ‘myofibroblasts,with high levels of a protein called ‘TAGLN’ when Fusobacterium was present.

The study also suggests that a potentially successful treatment method for endometriosis would involve taking antibiotics that specifically target this bacterium. However, it emphasizes that more research is needed to fully understand and verify this relationship between the bacteria infection and the health condition [2].

Evidence Supporting Fusobacterium-Induced Endometriosis

The study found that 64% of women with endometriosis had Fusobacterium in their endometrium compared to 7% of women without.

It also showed a higher Fusobacterium presence in the vaginal swabs obtained from women with endometriosis - further strengthening the importance of healthy vaginal microbiomes!

To further verify their claims, the researchers inoculated mice with Fusobacterium, an experiment that resulted in a significant increase in the number of endometriosis lesions. They also tested E. coli and Lactobacillus iners inoculation in mice, but these had no effect on the endometriotic lesions, emphasizing that Fusobacteria are the likely culprit [2].

How Does Fusobacterium Get to the Endometrium?

We don’t fully know this yet (as with many things related to endometriosis), but there are some theories:

Retrograde Menstruation

This is quite a controversial topic as retrograde menstruation is still seen as one of the main causes of endometriosis - however, most women experience it, even those without endometriosis.

The study suggests that retrograde menstruation, specifically in light of a pre-existing vaginal or uterine infection or microbiome dysbiosis, could facilitate the transfer of Fusobacterium into the endometrium [2].

Oral Transmission

Fusobacterium is present in the mouth and saliva of some individuals and is involved in gum disease. The bacteria kills the immune cells, thus facilitating the development of periodontal diseases.

The study suggests that Fusobacterium could be transmitted in the blood from the mouth to the uterus. They demonstrated this theory by introducing Fusobacteria to mice's jugular (a blood vessel in the neck) and found that 52% of the mice had Fusobacteria present in their endometrium after 2 weeks. This result suggests the bacteria had been carried there in the blood. It is also plausible that it could be transmitted there via the vagina [2].

Leaky Gut

Although not mentioned in this study, another potential hypothesis is the ‘leaky gut theory,’ which was previously linked to endometriosis.

A ‘leaky gut’ is typically an unhealthy gut (usually due to an unbalanced microbiome) that has lost its natural integrity and has become leaky, exposing the surrounding abdominal cavity to toxins and harmful bacteria. This theory could very much be at play here as Fusobacterium is commonly found in the gut microbiome [3].

How Effective Is Antibiotic Treatment Against Fusobacterium-Induced Endometriosis?

The study showed a significant reduction in endometriosis lesions when antibiotics were administered intra-vaginally and orally to mice with endometriosis.

The antibiotics used in the study were metronidazole (commonly used for bacterial vaginosis) and chloramphenicol. The findings in this study could be a real breakthrough in the battle against endometriosis, especially as metronidazole is already commonly used to treat vaginal infections.

However, it remains medically advisable not to overuse or misuse antibiotics, as antibiotic resistance is still a real threat [2].

What Are the Limitations of This Study?

The main limitation of this study is that it was carried out on mice and not humans. Mice don’t have menstrual cycles and are unlikely to develop endometriosis, hence the need for artificial induction.

Fusobacterium was also not found in all the respondents with endometriosis - only 64%. This reinforces that endometriosis is a multifaceted disease and does not favor a one-size-fits-all approach.

Lastly, the study also lacks direct evidence supporting the hypothesis that the presence of Fusobacterium in the endometrium promotes endometriosis after retrograde menstruation. In totality, it points to the need for more human-focused research on this topic [2].

What’s next?

This study has uncovered promising information that could help us better understand endometriosis, its causes, and how to manage it. As it’s all still in the early stages - you won’t see the antibiotic treatment option in the clinic for a while, but the research group is gearing up to start clinical trials on humans - a very promising next step in battling endometriosis [2].

When your vaginal microbiome is not in it’s optimal state, the microbes in your vaginal microbiome can lead to both vaginal infections and increased susceptibility to UTIs

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  1. Office on Women's Health. Endometriosis. 2021. Available from: https://www.womenshealth.gov/a-z-topics/endometriosis [Accessed 28th Jun 2023]
  2. Muraoka A, Suzuki M, Hamaguchi T, Watanabe S, Iijima K, Murofushi Y, Shinjo K, Osuka S, Hariyama Y, Ito M, Ohno K. Fusobacterium infection facilitates the development of endometriosis through the phenotypic transition of endometrial fibroblasts. Science Translational Medicine. 2023 Jun 14;15(700):eadd1531.
  3. Talwar C, Singh V, Kommagani R. The gut microbiota: a double-edged sword in endometriosis. Biology of Reproduction. 2022 Oct;107(4):881-901.

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