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Correlation of daptomycin bactericidal activity and membrane depolarization in Staphylococcus aureus
Jared A Silverman1, Nancy G Perlmutter, Howard M Shapiro
1Cubist Pharmaceuticals, Inc., Lexington, Massachusetts 02421, USA. jared.silverman@cubist.com
Antimicrobial Agents and Chemotherapy
|July 25, 2003
Summary
Daptomycin antibiotic action involves disrupting bacterial membrane potential, leading to rapid cell death. This study confirms a direct link between membrane depolarization and daptomycin
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Daptomycin is a lipopeptide antibiotic with a unique mechanism of action.
- Understanding daptomycin's precise mechanism is crucial for combating antibiotic resistance.
Purpose of the Study:
- To investigate the role of membrane potential in daptomycin's bactericidal activity.
- To establish a correlation between membrane depolarization and cell death induced by daptomycin.
Main Methods:
- Utilized fluorimetric and flow cytometric assays to measure membrane potential changes.
- Quantified bacterial viability and potassium ion release in response to daptomycin.
- Employed fluorescent probes to track ion movement across the bacterial membrane.
Main Results:
- Daptomycin (5 µg/ml) caused rapid and significant dissipation of membrane potential (>90%) in Staphylococcus aureus.
- Cell viability decreased by over 99% in parallel with membrane potential loss within 30 minutes.
- Demonstrated a dose-dependent relationship between daptomycin concentration, membrane depolarization, and cell death.
- Confirmed calcium-dependent potassium release triggered by daptomycin, correlating with bactericidal effects.
Conclusions:
- Dissipation of membrane potential is a key event in daptomycin's bactericidal mechanism.
- Daptomycin induces ion flux across the bacterial membrane, leading to cell death.
- A multistep model for daptomycin's action, involving membrane depolarization and ion release, is proposed.