Which STI can be treated with antibiotics and may cause pelvic inflammatory disease if left untreated?

Chlamydia is a bacterial sexually transmitted infection (STI) that is treatable with antibiotics. When left untreated, it can lead to serious complications, including pelvic inflammatory disease (PID). PID occurs when the infection spreads to the uterus and fallopian tubes, potentially resulting in long-term reproductive health issues such as infertility or chronic pain.

Chlamydia is often asymptomatic, especially in its early stages, which is why regular screening and prompt treatment are essential in preventing complications. Treatment typically involves antibiotics, which effectively clear the infection and reduce the risk of developing PID.

Other STIs mentioned involve different treatment protocols or consequences. For instance, syphilis, while also treatable with antibiotics, does not necessarily lead to PID in the same manner as chlamydia. Herpes, caused by a virus, is managed with antiviral medications but not cured by antibiotics, and HIV, another viral infection, has a complex treatment approach but is not associated with PID. Therefore, chlamydia is the correct answer based on its treatment options and potential complications.