Methicillin resistant staphylococci do not respond to b-lactam antibiotics because:
(Ref: KDT 6/e p700) Resistance to most penicillins is due to elaboration of beta-lactamase. Methicillin is most resistant penicilling to b-lactamase. Staphylococcus aureus develops resistance to methicillins by acquisition of altered pencillin binding proteins.