Methicillin-resistant staphylococci do not respond to β-lactam antibiotics because:
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.
They produce a b-lactamase which destroys methicillin and related drugs.
They elaborate an amidase which destroys methicillin and related drugs.
They are less permeable to b-lactam antibiotics.
None of the above