This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chemotherapy: General Principles, Subject name: Pharmacology
[{'content': 'A patient develops an infection of methicillin resistant Staphylococcus aureus. All of the following can be used to treat this infection except \nSelect and explain. \nA. Cotrimoxazole, B. Cefaclor, C. Ciprofloxacin, D. Vancomycin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (B) Cefaclor(Ref: KK Sharma 2/e p727)Cefaclor is a second generation cephalosporin and is not active against MRSA. Resistance in MRSA occurs due to altered PBPs (transpeptidase). As the binding site is altered, therefore, no beta lactam can bind and thus all beta-lactams (penicillins, cephalosporins, carbapenems and monobactams) are ineffective against MRSA. However, recently fifth generation cephalosporins like ceftaroline and ceftobiprol have been formed, which are effective against MRSA.', 'role': 'assistant'}]