One of the most common sexually transmitted infections (STIs), chlamydia is caused by an obligate intracellular bacterium, Chlamydia trachomatis. Clinical signs are often so mild that infected people may not recognize them, but the impact on the reproductive system, especially the female one, can be very severe. In particular, between 1% and 30% of women with untreated chlamydia infection may develop pelvic inflammatory disease (PID), which in 10%-20% of cases can lead to infertility. Permanent damage is observed less frequently in men, but some studies show a possible correlation between chlamydia infection and male infertility.