Which of the following is not mechanism for resistance to MRSA -

Option 1, 2 3 mechanisms for which staphylococcus aureus become resistant to methicillin: i) Presence of an acquired penicillin binding protein (PBP2a) ii) Modification of normal (Intrinsic) penicillin binding proteins MRSA is mediated by mecA gene; which is chromosomally coded. iii) Hyperproduction of b-lactamase - Rare Option 3 MRSA resistance is not absolutely b-lactamase independent. Resistance may also be produced by hyperproduction of beta-lactamase. Option 4 Intrinsic Resistance: It is the innate ability of a bacterium to resist a class of antibiotics. S. aureus doesn't show any intrinsic resistance. Enterococci show intrinsic resistance to cephalosporins and cotrimoxazole.