Answer:
They produce b-lactamase, an enzyme that destroys penicillins
They evade the antibiotic molecules by evading binding with antibodies
Step-by-step explanation:
MRSA bacteria is resistant to a class of penicillin like antibiotics called beta-lactams. Beta-lactams includes penicillin, methicillin, oxacillin, amoxicillin etc. These antibiotics have a common structural molecular component, a four atom beta-lactam ring. MRSA bacteria like Staphylococcus aureus produces beta-lactamase which destroys the beta-lactam ring hence destroying the antibiotic structure. It opens up the ring structure by hydrolysis which inactivates the antibacterial properties of antibiotic.
Another strategy by MRSA bacteria is to evade binding with antibiotics. Staphylococcus aureus have evolved with a novel antibiotic binding site called as PBP ( Penicillin Binding Site ) 2'. PBP2' has lower affinity for antibiotics so the bacteria can infect even in the presence of inhibitory concentration of antibiotic.