<prompt> How does staph aureus become resistant to methicillin:Heat shock proteinProtein ATranspeptidaseProtein C  <response>: Ans. c TranspeptidaseRef: Microbiology by Ananthanarayan and Paniker 8th ed. 197, 201-202Resistance develops due to alteration in transpeptidase penicillin binding protein on which all beta lactam antibiotics act- so MRSA is resistant to all b-lactam antibiotics. 