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.
They produce a b-lactamase which destroys methicillin and related drugs
They elaborate an amidase which destroys methicillin and related drugs
They have acquired penicillin binding protein which has low affinity for b-lactam antibiotics
They are less permeable to b-lactam antibiotics
Other topics and Adverse effects