Chlamydia Can Settle In The Intestine

Chlamydiae are sexually transmitted pathogens that can apparently survive for a long time in the human intestine. This is reported by researchers from Würzburg and Berlin in the journal PLOS Pathogens.

Chlamydia Becomes Increasingly Resistant to Antibiotics Over Time

Bacteria of the Chlamydia trachomatis strain are responsible for a number of serious diseases in humans. Chlamydia infections are the most common sexually transmitted diseases worldwide. Depending on the age group, it is estimated that up to ten percent of the world’s population is infected with the bacterium.

People who are infected with chlamydia can transmit these bacteria to other people during unprotected sex. The pathogens usually cause no or only mild symptoms at first, such as itching in the vagina, penis or anus. If the infection is noticed, it can be easily treated with antibiotics. If this is not done, the bacteria can cause serious problems, including infertility and cancer. If left untreated, a chlamydia infection in women can lead to blockage of the fallopian tubes, which can result in an ectopic pregnancy or infertility. Recent findings even suggest that chlamydia infections promote ovarian cancer. Men can become infertile after an infection.

A phenomenon is known from everyday clinical practice that can occur after successful antibiotic treatment: When people who have already been treated come to the doctor with a new chlamydia infection, they are often infected with exactly the same strains of bacteria as in the earlier infection.

“It is reasonable to assume that the bacteria find a niche in the body where they are not yet vulnerable, that they form a permanent reservoir there and can become active again later,” says Professor Thomas Rudel, chlamydia expert and head of the Department of Microbiology at the Biocenter of Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany. This phenomenon is known as persistence. It is problematic because the chlamydiae that persist in the body become increasingly resistant to antibiotics over time.

Intestinal Organoids that Have Been Experimentally Infected With Chlamydiae

In which niche do the bacteria persist? Experiments on mouse models have shown that chlamydia can survive in the intestines of animals. And in humans, too, the bacteria appear to settle in precisely this location. This is reported by the research groups of Thomas Rudel and Sina Bartfeld in the journal PLOS Pathogens. Professor Bartfeld worked at JMU until 2021; she now heads the Department of Medical Biotechnology at the Technical University of Berlin. The researchers identified the intestine as a niche with the help of miniature artificial organs, known as organoids. These are structures produced in the laboratory from human intestinal cells that are very similar in structure and function to the model organ.

The teams from Würzburg and Berlin tried to infect the intestinal organoids with chlamydia. They discovered that the inner cell layer of the organoids is very resistant to the bacteria: the pathogens could only penetrate there if the cell epithelium was damaged. From the blood side, however, the chlamydia were able to infect very efficiently. “In this case, we repeatedly found the persistent forms of the bacteria, which can be clearly identified with their typical shape under the electron microscope,” says JMU researcher Pargev Hovhannisyan, first author of the publication.

Transferred to the human organism, this would mean that a chlamydial infection with subsequent persistence would be difficult to spread via the inside of the intestine, but very easy via the blood. Whether this actually happens in the human body, however, still needs to be confirmed in clinical studies, according to Rudel. The next step for Thomas Rudel and Sina Bartfeld is to find out whether the chlamydiae select certain cell types for their persistence – no easy task, as the intestine consists of hundreds of different cell types. But perhaps it is also factors from the surrounding tissue that trigger persistence. These and other details are now to be investigated.