• Vancomycin is a structurally-unique and very large antibiotic that has activity only against gram positive bacteria.
Mechanism of Action
  • Vancomycin binds to the peptide component of peptidoglycan and physically prevents its cross-linking with the glycan component (See: bacterial cell wall). Thus, vancomycin ultimately disrupts peptidoglycan synthesis, similar to beta-lactam antibiotics. However, it does so by physical sequestration of the peptide precursor of peptidoglycan rather than inhibition of transpeptidase. Because vancomycin does not function by inhibiting transpeptidase it is impervious to bacteria which have developed resistance to beta-lactam antibiotics through alteration of transpeptidase (i.e. by acquiring altered penicillin binding proteins).
  • Vancomycin is a very large molecule and cannot pass through the outer membrane of gram negative bacteria; consequently, it is only effective against gram positive bacteria. However, because altered transpeptidase (Penicillin-binding Protein) does not affect the action of vancomycin, it is one of the few effective antibiotics for MRSA (Methicillin-resistant Staphylococcus aureus).
  • Vancomycin cannot be absorbed orally and must be given intravenously for systemic infections. However, for purely GI infections such as Clostridium difficile, oral vancomyin is sufficient.
Adverse Reactions
  • Red Man Syndrome: Vancomycin can induce release of histamine which can cause a syndrome of flushing if given rapidly
  • Ototoxicity: Can result in hearing loss
  • Nephrotoxicity: Can result in renal damage