This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'Which of the following organisms is most likely to be implicated as a cause of urethritis that persists after antibiotic therapy for gonorrhea? \nSelect and explain. \nA. Actinomyces, B. Chlamydia, C. Mycobacteria, D. Nocardia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Chlamydia, Mycoplasma, and Ureaplasma are not effectively treated by penicillins and cephalosporins, and are impoant causes of post-gonococcal urethritis. Chlamydial urethritis can be diagnosed by using fluorescent antibodies to identify inclusions in epithelial cells. Actinomyces is a mouth commensal that rarely causes a deeper oral infection. Mycobacteria cause chronic granulomatous diseases such as tuberculosis and leprosy. Nocardia can cause necrotizing pneumonia and disseminated disease.', 'role': 'assistant'}]