Oritavancin is a semisynthetic glycopeptide antibiotic that is an analog of vancomycin. It has bactericidal activity against Gram-positive bacteria.
|Mechanism of Action||
Like other glycopeptides and lipoglycopeptides, Oritavancin inhibits transglycosylation to stop peptidoglycan synthesis.
Its secondary mode of action is to interact directly with the cell membranes, causing depolarization which permeabilizes the membrane and causes cell death. This is attributable to the 4'-chlorobiphenylmethyl group.
|Spectrum||Effective against Gram-positive bacteria. It is effective at killing biofilm-producing pathogens like methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE).|
Oritavancin is commonly used in clinical in vitro microbiological antimicrobial susceptibility tests (panels, discs, and MIC strips) against Gram -positive isolates. Medical microbiologists use AST results to recommend antibiotic treatment options. Representative MIC values include:
S. aureus: 0.12 µ/ml - 4 µg/ml
For a complete list of Oritavancin MIC values, click here
Researchers studied the effect of polysorbate 80 on oritavancin binding to plastic surfaces and found it was rapidly lost from solution in susceptibility assay test plates. Greater losses were observed at lower concentrations suggesting saturable binding to surfaces. The inclusion of 0.002% Polysorbate 80 permitted the recovery of 80-100 % oritavancin, and it is suggested to use it in broth microdilution. It putatively blocks the nonspecific binding sites on he surfaces of the test vessels. The 16- to 32-fold reductions in the oritavancin MICs for the staphylococci and enterococci in the presence of polysorbate 80 are likely a result of polysorbate 80 inhibition of the binding of oritavancin to plastic surfaces. Investigators should use caution during in vitro and in vivo experiments to ensure proper assessment of the intended concentration. (Arhin et al, 2008).
Arhin FF et al (2008) Effect of polysorbate 80 on oritavancin binding to plastic surfaces: Implications for susceptibility testing. Antimicrob Agents Chemother. 52(5):1597-1603 PMID 18299406
Belley A et al (2010) Oritavancin disrupts membrane integrity of Staphylococcus aureus and vancomycin-resistant enterococci to effect rapid bacterial killing. Antimicrob. Agents Chemother. 54(12): 5369-5371
Zhanel GG, Schweizer F and Karlowsky JA (2012) Oritavancin: Mechanism of action. Clin. Infect. Dis. 54(suppl 3):S214–S219