This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
[{'content': 'Prophylactic drug of choice for diphtheria is: \nSelect and explain. \nA. Tetracycline, B. Cefaclor, C. Ceftriaxone, D. Erythromycin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Penicillin and erythromycin are the only antibiotics recommended for treatment. Both antibiotics are equally effective in resolving fever and local symptoms. However, erythromycin has been shown to be marginally superior. DOC- for carriers or for prophylaxis- Erythromycin for 10- 14 days.', 'role': 'assistant'}]