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
Methicillin-resistant staphylococci do not respond to β–lactam antibiotics because : 
Select and explain. 
A. They produce a β–lactamase which destroys methicillin and related drugs, B. They elaborate an amidase which destroys methicillin and related drugs, C. They have acquired penicillin binding protein which has low affinity for β-lactam antibiotics, D. They are less permeable to β-lactam antibiotics
C: They have acquired penicillin binding protein which has low affinity for β-lactam antibiotics
Answer: C: They have acquired penicillin binding protein which has low affinity for β-lactam antibiotics 
Explanation: Resistance to most penicillins is due to elaboration of beta-lactamase.
Methicillin is most resistant penicillin to β-lactamase.
Staphylococcus aureus develops resistance to methicillin by the acquisition of altered penicillin-binding proteins.