Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed,^{[citation needed]} although the emergence of vancomycin-resistant organisms means that it is increasingly being displaced from this role by linezolid (Zyvox) available PO and IV and daptomycin (Cubicin) IV and quinupristin/dalfopristin(Synercid) IV.

Vancomycin acts by inhibiting proper cell wall synthesis in Gram-positive bacteria. Due to the different mechanism by which Gram-negative bacteria produce their cell walls and the various factors related to entering the outer membrane of Gram-negative organisms, vancomycin is not active against Gram-negative bacteria (except some non-gonococcal species of Neisseria).

The large hydrophilic molecule is able to form hydrogen bond interactions with the terminal D-alanyl-D-alanine moieties of the NAM/NAG-peptides. Under normal circumstances, this is a five-point interaction. This binding of vancomycin to the D-Ala-D-Ala prevents cell wall synthesis in two ways. It prevents the synthesis of the long polymers of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) that form the backbone strands of the bacterial cell wall, and it prevents the backbone polymers that do manage to form from cross-linking with each other.^[

Indications

Vancomycin is indicated for the treatment of serious, life-threatening infections by Gram-positive bacteria that are unresponsive to other less-toxic antibiotics. In particular, vancomycin should not be used to treat methicillin-sensitive Staphylococcus aureus because it is inferior to penicillins such as nafcillin.^[15][16]

The increasing emergence of vancomycin-resistant enterococci has resulted in the development of guidelines for use by the Centers for Disease Control (CDC) Hospital Infection Control Practices Advisory Committee. These guidelines restrict use of vancomycin to the following indications:^[17][18]

• Treatment of serious infections caused by susceptible organisms resistant to penicillins (methicillin-resistant Staphylococcus aureus and multi-resistant Staphylococcus epidermidis (MRSE)) or in individuals with serious allergy to penicillins
• Treatment of Pseudomembranous colitis caused by the bacterium Clostridium difficile; in particular, in cases of relapse or where the infection is unresponsive to metronidazole treatment (for this indication, vancomycin is given orally, rather than via its typical, I.V. route)
• For treatment of infections caused by gram-positive microorganisms in patients with serious allergies to beta-lactam antimicrobials.^[18]
• Antibacterial prophylaxis for endocarditis following certain procedures in penicillin-hypersensitive individuals at high risk^[18]
• Surgical prophylaxis for major procedures involving implantation of prostheses in institutions with a high rate of MRSA or MRSE^[18]
• Early in treatment as an empiric antibiotic to cover for possible MRSA infection while waiting for culture identification of the infecting organism.