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 b-lactamase which destroys methicillin and related drugs., B. They elaborate an amidase which destroys methicillin and related drugs., C. They are less permeable to b-lactam antibiotics., D. None of the above
B: They elaborate an amidase which destroys methicillin and related drugs.
Answer: B: They elaborate an amidase which destroys methicillin and related drugs. 
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 methicillins by acquisition of altered penicillin binding proteins.