This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infection, Subject name: Medicine
Rx of latent syphilis- 
Select and explain. 
A. Penicillin, B. Erythromycin, C. Tetracycline, D. Ciprofloxacin
A: Penicillin
Answer: A: Penicillin 
Explanation: Stage of Syphilis Patients without Penicillin Allergy Patients with Confirmed Penicillin Allergy Primary, secondary, or early latent CSF normal or not examined: Penicillin G benzathine(single dose of 2.4 mU IM)CSF abnormal: Treat as neurosyphilis CSF normal or not examined: Tetracycline HCl(500 mg PO qid) or doxycycline (100 mg PO bid)for 2 weeksCSF abnormal: Treat as neurosyphilis Late latent (or latent of unceainduration), cardiovascular, or benignteiary CSF normal or not examined: Penicillin G benzathine(2.4 mU IM weekly for 3 weeks)CSF abnormal: Treat as neurosyphilis CSF normal and patient not infected with HIV:Tetracycline HCl (500 mg PO qid) or doxycycline(100 mg PO bid) for 4 weeksCSF normal and patient infected with HIV:Desensitization and treatment with penicillin if compliancecannot be ensuredCSF abnormal: Treat as neurosyphilis (Harrison's Principles of internal medicine, 20 th edition, page 1387)