The bacteria behind chlamydia can colonize the gut, and from that hiding place, they may act as a source of repeated infections, new research using miniature intestines suggests.

Chlamydia is the most common sexually transmitted infection (STI) worldwide. The form of the infection that affects humans is caused by a species of bacteria known as Chlamydia trachomatis.

The disease most often affects the genital region, sometimes causing pain and unusual discharge from the vagina or penis. However, over the years, research in mice and various clinical reports in humans have suggested that C. trachomatis may also be able to infect the human digestive tract. This means that, theoretically, the bacteria could hide in the gut and then cause repeated genital infections, which commonly occur in patients despite treatment with antibiotics.

Yet, until now, scientists haven’t been able to test this theory in human cells.