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': 'Microorganisms may develop resistance to various drugs by: \nSelect and explain. \nA. Decreased drug affinity for the target., B. Elaboration of the enzymes which inactivate the drug., C. Development of alternative metabolic pathway., D. All of the above.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Decreased affinity for the target e.g. pneumococci and staphylococci may develop\xa0altered penicillin binding proteins.\nDevelopment of alternative metabolic pathway e.g. sulfonamide resistant\xa0organisms start utilizing preformed folic acid in place of synthesizing it from\xa0PABA.\nElaboration of the enzymes which inactivate the drug e.g. β-lactamases (penicillins\xa0and cephalosporins), chloramphenicol acetyl transferase (chloramphenicol) and\xa0aminoglycoside inactivating enzymes (aminoglycosides).\nDecreased drug permeability due to the loss of specific channels e.g. aminoglycosides\xa0and tetracyclines attain much lower drug concentration in the resistant organisms\xa0than in the sensitive organisms.\nDevelopment of efflux pumps (tetracyclines, erythromycin and fluoroquinolones)\xa0results in active extrusion of the drug from the resistant microorganisms.', 'role': 'assistant'}]