Which bacterium causes chlamydia, one of the most common sexually transmitted infections?

Chlamydia trachomatis causes chlamydia, one of the most common sexually transmitted infections. It is an obligate intracellular bacterium, meaning it must reproduce inside the cells of its host rather than growing independently in ordinary laboratory culture.

Many genital infections cause no noticeable symptoms, especially in women, but untreated infection can lead to pelvic inflammatory disease, ectopic pregnancy, or infertility. In men, complications can include epididymitis. The bacterium can also infect the rectum, throat, and eyes, and transmission from an infected mother to a newborn can cause conjunctivitis or pneumonia.

C. trachomatis is different from Neisseria gonorrhoeae, the bacterium responsible for gonorrhea, although the infections can occur together. Modern diagnosis commonly uses nucleic acid amplification tests on urine or swab samples. Appropriate antibiotics can cure the infection, but reinfection is common when partners are not tested and treated.