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An Antibiotic May Treat Endometriosis

July 02, 2019
By CRM Orlando

Investigators at Washington University School of Medicine in St. Louis have found that treatment with the antibiotic, Metronidazole, reduces the size of endometriotic lesions. The mechanism is thought to involve reduction of the gut microbes that may be causative of the disease. Although this study was performed in mice, the researchers are planning a large, multicenter clinical trial to test the drug metronidazole in women.

Endometriosis is a chronic inflammatory condition that affects up to 10 percent of reproductive age women and up to 45% of patients who frequent an infertility clinic.  More than 175 million women worldwide are thought to be affected. The condition results from uterine lining (endometrial) cells refluxing into the pelvic-abdominal cavity. These estrogen-dependent lesions tend to be self-propagating and defiant of the immune system.  Current treatments are both medical (hormone therapy) and surgical; however, both approaches involve potential side effects, risks, and disease recurrence.

The St. Louis group found that treating mice with metronidazole reduced the size of endometriosis-related lesions, whether treatment was started before the lesions began or after endometriosis was already well-formed. The findings also suggest that bacteria in the gut (microbiome) play a role in the progression of the disease.

An additional finding off the study was that some of the gut bacteria associated with bowel problems are also associated with endometriosis. When mice were treated with the broad-spectrum antibiotic metronidazole, not only were the endometriosis lesions reduced in size but bowel inflammation also was reduced. (It is well-known that reproductive-aged women with inflammatory bowel disease are more likely to develop endometriosis.)

Other antibiotics were also tested; however, ampicillin, neomycin and vancomycin did not diminish endometriotic lesions or bowel inflammation. Furthermore, the research team found that levels of a protective type of gut bacteria were very low in the mice with endometriosis, so that following antibiotics, it may be possible to employ probiotics to boost levels of the protective bacteria. This work opens the door to identifying gut bacteria that can promote or prevent endometriosis and may become a path to simpler methods for diagnosing endometriosis.

Although human studies have not yet been performed, there is a huge and growing body of  human studies to suggest that a healthy gut with diverse bacterial species affects general health, susceptibility to disease and the burden of disease.  A diet rich in probiotics may have a protective effect upon endometriosis.


Sangappa B Chadchan, Meng Cheng, Lindsay A Parnell, Yin Yin, Andrew Schriefer, Indira U Mysorekar, Ramakrishna Kommagani. Antibiotic therapy with metronidazole reduces endometriosis disease progression in mice: a potential role for gut microbiota. Human Reproduction, 2019; DOI: 10.1093/humrep/dez041

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