Answer:
S. aureus acquire resistance by :
1) Beta-lactamase production.
2) Changes in penicillin-binding protiens (PBP) (mecA genes encode these altered PBPs )
3) Genes encoding the enzymes substituting D-lactate for D-alanine in the peptidogylcan.
Explanation:
More than 90% strains of Staphylococcus aureus contains plasmids which code for beta- lactamases which cause the enzymatic hydrolysis of the beta lactam ring resulting in the loss of antibacterial activity. (Resistance against penicillins )
Some of the strains of S.Aureus are resistant to beta lactamase resistant penicillins such as methicilin (MRSA) and nafcillin (NRSA) by virtue of changes in the penicillin-binding protien (PBP) in their cell membrane.
Some strains of S.Aureus are resistant to Vancomycin (VRSA) and they acquire this resistance by some genes located in a transposon on a plasmid and encode the enzymes that substitute D-lactate for D-alanine in the peptidoglycan.