Which organism is primarily associated with PID in the presence of an IUD?

The organism primarily associated with pelvic inflammatory disease (PID) in the context of an intrauterine device (IUD) is Actinomyces israelii. This organism is part of the normal flora of the vagina and can enter the uterus, particularly when there are situations that allow for its introduction, such as during the placement of an IUD.

Actinomyces israelii is notable because it can form a biofilm on the surface of the IUD, which can act as a niche for infection. While Chlamydia trachomatis and Neisseria gonorrhoeae are also common pathogens responsible for PID, they are not specifically linked to the presence of an IUD in the same way. Instead, they are more broadly associated with sexually transmitted infections.

Escherichia coli, though associated with urinary tract infections, is less commonly known for causing PID in this context. The unique association of Actinomyces israelii with IUDs makes it a significant organism to consider when evaluating the risk of PID in patients with these devices.