<prompt> Which of the following is not a mechanism for resistance to MRSA -Resistance is chromosomally mediatedProduced mainly by alteration in PBPsMRSA resistance is absolutely beta lactamase dependentIntrinsic resistance is known  <response>: In the previous explanation, I have explained the mechanism of antibiotic resistance in general for all staphylococci species.Antibiotic resistance specific to MRSA:-Mechanism of resistance of MRSA There are three known mechanisms for which Staphylococcus aureus become resistant to methicillin:-Presence of penicillin-binding protein PBP 2a Most casesModification of normal intrinsic penicillin-binding proteinHyperproduction of beta-lactamase rareS. aureus strains have four intrinsic penicillin-binding proteins PBPs which have a high affinity for beta-lactam antibiotics.PBP2a is an inducible acquired protein that is produced only by MRSA; it is not an intrinsic PBP.PBP2a has a very low affinity for beta-lactam antibiotics S.aureus strains containing PBP2a i.e.MRSA are resistant to all beta-lactam antibioticsProduction of PBP2a is chromosomally mediated. Now see each option of question:Resistance to MRSA is chromosomally mediated and involves the production of an altered penicillin-binding protein PBP2a.MRSA resistance is not absolutely beta-lactamase dependent. Though altered penicillin-binding protein is involved in most strains, rarely beta-lactamase production is also involved.Intrinsic resistance is known, that means an alteration in intrinsic PBPs is also one of the mechanisms for resistance in MRSA. reminding you PBP2a is not an intrinsic PBP, it is an acquired PBP. 