TABLE 2.

Summary of antibiotic resistant mechanisms in MRSA.

Antibiotic class	Resistant mechanism
Penicillins and 4 generation of Cephalosporins	Penicillinase, production of PBP2a
Carbapenems	Development of PBP2a
Tetracyclines	Ribosomal methylation of binding sites, efflux pumps
Tigecyclines	Efflux pumps
Macrolides and clindamycin	Ribosomal methylation of binding sites, efflux pumps
Fluoroquinolones	Mutations in topoisomerase IV and DNA gyrase, efflux pumps
Rifampicin	Mutations in RNA polymerase gene
TMP/SMX	Mutations in DHPS and DHFR
Aminoglycosides	Aminoglycoside degradation enzymes
Daptomycin	Electrostatic repulsion through increase to the cell-surface charge
Vancomycin	VRSA: altered structure of peptidoglycan precursors from D-Ala-D-Ala to D-Ala-D-Lac; VISA: increased production of peptidoglycan, thicker cell wall, decoy D-Ala-D-Ala dipeptides on cell surface
Linezolid	Mutations to the 23S rRNA, altering required modifications to the 23S rRNA, mutations to the 50S ribosomal L3 protein

Abbreviations: PBP, penicillin binding protein; TMP/SMX, trimethoprim-sulfamethoxazole; DHPS, dihydropteroate synthase; DHFR, dihydrofolate reductase.