In a study published Wednesday in the journal Science Translational Medicine, Japanese researchers analyzed vaginal swab samples from 155 women — 76 healthy women and 79 women with endometriosis. They found that 64 percent of women with endometriosis tested positive for bacteria in the genus Fusobacterium. Fewer than 10 percent of healthy women carried the bacteria in the uterus.
After the initial discovery, the researchers used mouse models to further investigate the link. They found an increase in endometriotic lesions after mice were injected with fusobacterium. When they gave the mice antibiotics, the number and weight of the lesions decreased significantly.
Some strains of Fusobacterium are harmless, but others can cause serious infections in humans. Fusobacterium is associated with oral diseases such as periodontitis and tonsillitis, but this is the first time the bacteria has been linked to problems in the female reproductive system.
One of the study authors, Yutaka Kondo, a cancer biologist at Nagoya University Graduate School of Medicine in Japan, described the discovery as a breakthrough in the field of women’s health care.
“Before, no one thought that endometriosis came from a bacterial infection, so this is a very new idea,” Kondo said.
Endometriosis is a condition where tissue similar to the lining of the uterus grows outside the uterus. Ulcers cause painful menstrual cramps and digestive problems and can lead to infertility. Previous research suggests that retrograde menstruation may be influenced by a genetic predisposition or hormones, although no one knows the exact cause.
Birth control, a hormonal option that stops a person’s period, is one of the treatments for endometriosis. But it is effective only when a person takes the pill. As soon as they stop the medication they are trying to get pregnant, the pain starts again. And since 30 to 50 percent of people with endometriosis experience infertility, they may spend months trying to get pregnant while living in excruciating pain.
The only “cure” for endometriosis is to remove a person’s reproductive organs.
Allison K., a reproductive endocrinologist at the Fertility Center of Illinois who was not involved in the study. “Medicine puts a Band-Aid on it,” Rodgers says.
“I can give you medicine to stop your period; I can give you birth control pills; I can give you pain medicine; I can cut it out surgically,” she said. “But we haven’t figured out the cause, and once we start to figure out the cause, we can design targeted approaches to treatment.”
Although no definitive treatment can be derived from this new study, Kondo emphasizes that the discovery will spur research into more potential treatments.
“If this is indeed true for other patients, it would be worth examining the microbiome of endometriosis patients from a larger population and assessing whether there is a combination of different infectious agents that cause inflammation and act on tissue like endometriosis,” Raymond said. Manohar Anjan is director of the Stem Cell Biology and Regenerative Medicine Research Laboratory at Brigham and Women’s Hospital in Boston.
Anjan, who specializes in endometriosis, says he would be “surprised” if there was an absolute correlation and that it “warrants more investigation.”
Anjan and Rodgers note that the sample size was small, and stated that the study results do not automatically recommend antibiotics for patients with endometriosis.
Still Rodgers similarly describes results “even if they are in their infancy.” She and other experts believe this is a jumping-off point for further research.
“Studies like this are exciting — for every 1,000 people, maybe only one makes a breakthrough,” Rodgers said. “But once we figure out why some people’s endometrial cells are extra sticky, we can look at targets for cures.”