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Oritavancin activity against Staphylococcus aureus causing invasive infections in U.S. and European hospitals: a
Rodrigo E Mendes1, Helio S Sader, Robert K Flamm
1JMI Laboratories, North Liberty, Iowa, USA.
Abstract:
In this study, oritavancin had modal MIC, MIC50, and MIC90 values of 0.03, 0.03, and 0.06 μg/ml, respectively, against Staphylococcus aureus. Similar results (MIC50/90, 0.03/0.06 μg/ml) were observed against methicillin-resistant and -susceptible isolates and those demonstrating multidrug-resistant (MDR) and non-MDR phenotypes. When oritavancin (MIC50/90, 0.06/0.12 mg/ml) was tested against S. aureus with elevated MIC values for daptomycin (i.e., 1 to 4 mg/ml) and vancomycin (i.e., 2 mg/ml), it showed MIC results 2-fold higher than those for the more susceptible vancomycin or daptomycin counterparts (MIC50/90, 0.03/0.06 mg/ml), yet it inhibited these isolates at ≤0.25 mg/ml.
Insights
Oritavancin demonstrates potent activity against Staphylococcus aureus, including difficult-to-treat strains. This lipoglycopeptide antibiotic shows consistent efficacy, even against bacteria with resistance to other drugs.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Staphylococcus aureus is a significant human pathogen, responsible for a wide range of infections.
- The emergence of antibiotic resistance, including methicillin resistance (MRSA) and multidrug resistance (MDR), poses a major clinical challenge.
- Oritavancin is a lipoglycopeptide antibiotic with activity against Gram-positive bacteria.
Purpose of the Study:
- To evaluate the in vitro antimicrobial activity of oritavancin against Staphylococcus aureus.
- To assess oritavancin's efficacy against methicillin-resistant and -susceptible S. aureus strains.
- To determine oritavancin's activity against S. aureus isolates with reduced susceptibility to daptomycin and vancomycin.
Main Methods:
- Determination of Minimum Inhibitory Concentration (MIC) values for oritavancin.
- Testing against various phenotypes of Staphylococcus aureus, including MDR and non-MDR isolates.
- Comparative analysis of oritavancin's MIC values against S. aureus with elevated MICs for daptomycin and vancomycin.
Main Results:
- Oritavancin exhibited low modal MIC, MIC50, and MIC90 values (0.03, 0.03, and 0.06 μg/ml) against Staphylococcus aureus.
- Similar potent activity was observed against methicillin-resistant/susceptible and MDR/non-MDR S. aureus isolates.
- Oritavancin maintained inhibitory activity (≤0.25 mg/ml) against S. aureus with elevated MICs for daptomycin and vancomycin.
Conclusions:
- Oritavancin demonstrates broad and potent in vitro activity against a wide range of Staphylococcus aureus isolates.
- The drug retains efficacy against strains with resistance mechanisms, including those conferring reduced susceptibility to vancomycin and daptomycin.
- These findings support oritavancin's potential as a therapeutic option for S. aureus infections, including those caused by resistant strains.
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