The bacteria that cause chlamydia may be nastier than we knew. In a new study published this week, scientists have found evidence that these bacteria lurk in the gut. The discovery, the researchers say, may explain why chlamydia recurs in some people even after successful antibiotic treatment.
Human chlamydia is Chlamydia trachomatis (Other animals, like koalas, have their own versions of chlamydia.) It’s the most commonly reported sexually transmitted disease in the United States, with more than 1.6 million recorded cases in 2022. While most infected people don’t get sick, some experience scary symptoms like bloody urine, genital discharge, and rectal pain or bleeding, depending on the site of infection. If left untreated, chlamydia can lead to life-altering complications, including pelvic inflammatory disease, arthritis, and infertility, and it also increases your risk of contracting other sexually transmitted diseases.
The new study was led by researchers at the University of Würzburg in Bavaria, Germany, who hoped to get to the bottom of a persistent mystery surrounding chlamydia. Although the infection can be treated with antibiotics (for now, at least), some people later end up seeing a doctor because their chlamydia has returned. When scientists looked into these cases, they found that sometimes people were reinfected with a strain of bacteria that was genetically identical or very similar to the one that originally infected them.
Some of these cases may actually be the result of infections that weren’t fully treated, sex with an untreated partner who spread the infection in the first place, or playing with previously used and contaminated sex toys (this is unlikely, since the bacteria don’t survive very long outside the body.) But some research also suggests that the chlamydia bacteria can form hidden reservoirs elsewhere in the body that can cause problems again when the conditions are right.
Other related species Chlamydia trachomatis Chlamydia is known to reside in the intestines of its hosts, where our own chlamydia bacteria may lurk. But to date, studies showing that chlamydia can become persistent have been conducted mainly in animals. The new study, published this month in the journal Nature, suggests that chlamydia can be transmitted to humans through bacteria. PLOS PathogensResearchers say they are now closer to proving that this can actually happen in humans.
Scientists grew human intestinal organoids, miniature versions of human organs and tissues, in the lab and tested whether the bacteria Chlamydia could infect them. The organoids were made to resemble the layer of cells that lines the inside of the intestine. The researchers found that bacteria were not very good at infecting the “apical” surface of the organoids, the layer of the organ that is exposed to the outside environment. But the bacteria could easily infect the intestinal organoids through their “basolateral” surface, the layer of cells that connects to other underlying tissues and structures, including blood vessels. And when the researchers looked more closely at the bacteria that infected these organoids, they found a familiar foe.
“In this case, we have repeatedly found a persistent morphology of the bacterium, whose typical shape is clearly discernible under an electron microscope,” lead researcher Pargev Hovhannisyan, head of the microbiology department at the University of Würzburg, said in a university statement.
The researchers caution that this finding alone is not conclusive evidence that chlamydia lurks in the gut, and more research is needed to confirm and better understand the phenomenon. If this risk is real, there are other questions to answer, such as how chlamydia bacteria get into the gut and the specific cells in which they prefer to hide. But whatever is learned shouldn’t change the way sexually active people protect themselves against these bacteria. It’s still important to get tested for chlamydia and other STIs regularly (at least annually, but more frequently if you have multiple partners), consider continuing to use barrier methods such as condoms, and complete a full course of antibiotics if you have chlamydia.
