A 32-year-old woman consults her gynecologist for fever and progressively severe pain in her left lower abdominal quadrant. The pain began several days ago, sholy after the onset of her menses. Pelvic examination demonstrates bilateral adnexal tenderness, much more marked on the left than the right. Which of the following is the most likely pathogen?

This patient has pelvic inflammatory disease, which typically involves both right and left fallopian tubes, although one side may be more severely infected. The most common causative organisms are Neisseria gonorrhoeae and Chlamydia trachomatis. The condition may present acutely (as in this case) or insidiously. Timely diagnosis and treatment are impoant to prevent gynecologic morbidity that may include infeility, ectopic pregnancy, and chronic pelvic pain. Escherichia is a bowel organism that is more likely to infect the urinary tract than the fallopian tubes. Staphylococcus tends to colonize the nasopharynx and skin, and is more likely to cause infection in the skin or respiratory tract. Streptococcus tends to infect the respiratory tract and skin.