A 24-year-old woman comes to the office due to lower abdominal pain and malodorous vaginal discharge. The patient has had increasing vaginal discharge for the past 3 weeks and increasing lower abdominal pain for the last few days. She has no chronic medical conditions or medication allergies. The patient is sexually active and uses a copper-containing intrauterine device for contraception. Temperature is 38.3 C (100.9 F), blood pressure is 110/70 mm Hg, and pulse is 78/min. The lower abdomen is tender to palpation with no rebound or guarding. On pelvic examination, the strings of the intrauterine device are seen, and cervical motion tenderness and mucopurulent cervical discharge are present. Culture of the discharge shows thin, elongated, gram-positive bacilli in an acute-angle branching pattern. Which of the following is the most appropriate pharmacotherapy for this patient?
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This patient with fever, abdominal pain, and mucopurulent cervical discharge has pelvic inflammatory disease (PID). PID is typically treated with empiric broad-spectrum antibiotics (eg, ceftriaxone plus doxycycline) to cover the most common pathogens (ie, Chlamydia trachomatis, Neisseria gonorrhoeae).
However, patients with long-term intrauterine devices (IUDs) are at increased risk for developing an active Actinomyces infection, as evidenced by this patient's culture that reveals acute-angle branching, gram-positive bacilli. Actinomyces is a facultative anaerobic bacterium and part of normal gastrointestinal flora. Because of the proximity of the anus to the vagina, lower genital tract colonization with Actinomyces is common in women. The bacteria can ascend to the upper genital tract to colonize an indwelling IUD.
An Actinomyces infection is difficult to eradicate in the presence of a foreign body; therefore, IUD removal is required. In addition to empiric broad-spectrum antibiotics, patients need targeted antibiotic pharmacotherapy with penicillin, which works by binding penicillin-binding proteins, blocking transpeptidase formation in the cell wall, and activating autolytic enzymes.
(Choice A) Fluconazole is an antifungal commonly used to treat Candida albicans; when cultured, C albicans forms smooth, cream-colored colonies consisting of branching pseudohyphae and blastoconidia (ie, buds).
(Choice B) Metronidazole can be used to treat anaerobic infections such as Trichomonas vaginalis and Gardnerella vaginalis (ie, bacterial vaginosis), which are typically diagnosed on wet mount microscopy. T vaginalis appears as motile, flagellated trophozoites; bacterial vaginosis can be identified by clue cells (ie, squamous epithelial cells covered with bacteria). Although Actinomyces is a facultative anaerobe, most isolates are resistant to metronidazole.
(Choice C) Nitrofurantoin achieves high, bactericidal concentrations in urine. Therefore, it is used to treat uncomplicated urinary tract infections (UTIs), which are most commonly caused by Escherichia coli, a gram-negative rod.
(Choice E) Trimethoprim-sulfamethoxazole is ineffective against Actinomyces. It is commonly used to treat Nocardia, which has the classic appearance of filamentous, wide-branching, gram-positive rods rather than rods with acute-angle branching as seen in Actinomyces.
Educational objective:
Actinomyces is an anaerobic, gram-positive bacillus with acute-angle branching. It can colonize intrauterine devices (IUDs) and may cause pelvic inflammatory disease (eg, fever, abdominal pain, mucopurulent cervical discharge). Treatment is with IUD removal and penicillin.