Pelvic inflammatory disease is most commonly associated with infection by which pathogens?

• A. Escherichia coli and Klebsiella pneumoniae
• B. Chlamydia trachomatis and Neisseria gonorrhoeae
• C. Gardnerella vaginalis and Candida albicans
• D. Mycoplasma hominis and Ureaplasma urealyticum

Answer: (B)

Pelvic inflammatory disease is an ascending infection of the upper female genital tract, most often starting with a cervicitis caused by sexually transmitted bacteria. The two pathogens most classically linked to PID are Neisseria gonorrhoeae and Chlamydia trachomatis. Neisseria gonorrhoeae causes cervicitis and can spread upward to involve the endometrium and fallopian tubes, leading to salpingitis and endometritis. Chlamydia trachomatis often causes cervicitis and can be asymptomatic; it also readily ascends and inflames the uterine and tubal tissues. Because these organisms frequently be transmitted sexually and have a strong tendency to ascend, they are the best-known culprits behind PID. In reality, PID is often polymicrobial, with additional anaerobes and other genital tract bacteria contributing, but the combination of gonorrhea and chlamydia remains the classic association. The other options describe organisms more commonly linked to bacterial vaginosis, yeast infections, or nonclassical pelvic infections, rather than the primary pathogens classically tied to PID.