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: Pharmacology
[{'content': 'Which of the following is not an established antimicrobial drug synergism at the clinical level? \nSelect and explain. \nA. Amphotericin B and flucytosine in cryptococcal meningitis, B. Carbenicillin and gentamicin in pseudomonal infections, C. Penicillin and tetracycline in bacterial meningitis, D. Trimethoprim and sulfamethoxazole in coliform infections', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Combination of a bacteriostatic and a bactericidal drug in most cases is antagonistic. Bactericidal drugs act on fast multiplying organisms whereas bacteriostatic drugs inhibit the growth. Here, penicillin is bactericidal whereas tetracyclines are bacteriostatic.', 'role': 'assistant'}]