MEDizzy - A 34-year-old man presented to the clinic with a painful

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BACTERIAL CELL WALL SYNTHESIS INHIBITORS

A 34-year-old man presented to the clinic with a painful ulcer on his penis. Regional lymph nodes were enlarged and painful. The man admitted to unprotected intercourse with a new partner while on a recent vacation. Darkfield microscopy and an FTA-ABS (fluorescent treponemal antibody absorption) test for syphilis were negative. A Gram stain of pus revealed short gram -negative bacilli in parallel chains. Which of the following would be the most appropriate pharmacotherapy for this patient?

ExplanationThe correct answer is D. The history of the patient and the site of the ulcer suggest a sexually transmitted disease. Among these diseases, those characterized by ulcer on the penis include chancroid (caused by Haemophilus ducreyi), lymphogranuloma venereum (caused by Chlamydia trachomatis), granuloma inguinale (caused by Donovania granulomatis), syphilis (caused by Treponema pallidum), and genital herpes (caused by herpes simplex virus). The presence of gram-negative bacilli excludes viral infections such as genital herpes, as well as chlamydia and donovania infections (chlamydia and donovania are intracellular bacteria). Syphilis is unlikely because of the negative darkfield microscopy and FTA-ABS (fluorescent treponemal antibody absorption) test. Therefore, the patient’s disease is most likely caused by H. ducreyi, a gram-negative bacterium that is sensitive to second- and third-generation cephalosporins, trimethoprim-sulfam etoxazole, quinolones, and tetracyclines. Ceftriaxone is most often used because it has a long half-life (about 7 hours) and therefore can provide a long minimum bactericidal concentration (most β-lactam antibiotics exhibit time-dependent killing). A−C These antibiotics are not effective against gram-negative bacteria.