A 31-year-old, sexually active woman has had a mucopurulent vaginal discharge for 1 week. On pelvic examination, the cervix appears reddened around the os, but no erosions or mass lesions are present. A Pap smear shows numerous neutrophils, but no dysplastic cells. A cervical biopsy specimen shows marked follicular cervicitis. Which of the following infectious agents is most likely to produce these findings?

The inflammatory cells in the cervical discharge with redness (erythema) and the biopsy findings indicate that the patient has cervicitis. Chlamydia trachomatis is the most common cause of cervicitis in sexually active women. Candidiasis, gonorrhea, and trichomoniasis also are common. Candidiasis often produces a scant, white, curd-like vaginal discharge; gonorrhea may have associated urethritis; and Trichomonas may produce a profuse homogeneous, frothy, and adherent yellow or green vaginal discharge. Gardnerella is found in bacterial vaginosis, a common condition caused by an overgrowth of bacteria. Gardnerella infection produces a moderate, homogeneous, low-viscosity, adherent vaginal discharge that is white or gray and has a characteristic fishy odor; clue cells are seen on a wet mount. Herpetic infections are more likely to manifest as clear vesicles on the skin in the perineal region. Infection with human papillomavirus is associated with condylomata, dysplasia, and carcinoma.