VANCOMYCIN Mechanism of Action Vancomycin is an antibiotic drug which is structurally classified as a glycopeptide. It mainly acts by prevention of cell-wall biosynthesis of bacteria. It is specially effective against gram-positive bacteria and has been known to be effective against resistant strains of MRSA. Vancomycin is known as the drug of last resort as it generally used when all other treatments have failed. However, bacteria have started developing resistance to vancomycin as well- leading to use of other antibiotics. Vancomycin acts by inhibiting cell wall synthesis of bacteria. Peptidoglycan layer of the cell wall is rigid due to its highly cross-linked structure. During the synthesis of the peptidoglycan layer of bacteria, new building blocks of peptidoglycan get inserted (i.e. monomers of N-acetylmuramic acid and N-acetylglucosamine) into the membrane.Vancomycin inhibit the synthesis of bacterial cell wall phospholipids as well as peptidoglycan polymerization in a time dependent fashion by binding to the D-ala-D-ala side chain of the precursor pentapeptide.This prevent the transglycosylation step in peptidoglycan polymerization . By doing so, vancomycin makes the peptidoglycan layer less rigid and more permeable. This causes cellular contents of the bacteria to leak out and eventually death of the bacteria. Mutations in the transpeptidase enzyme can lead to increased resistance to vancomycin.