SILVERMAN JA, PERLMUTTER NG, SHAPIRO HM; Interscience Conference on Antimicrobial Agents and Chemotherapy (41st : 2001 : Chicago, Ill.).
Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 2001 Dec 16-19; 41: abstract no. C1-1800.
Cubist Pharma- ceuticals, Cambridge, MA
Daptomycin is a novel lipopeptide antibiotic currently undergoing Phase II and III clinical trials. It has potent bactericidal activity against Gram-positive pathogens. The site of action is the bacterial cytoplasmic membrane, but the mechanism of action remains to be characterized. Previous research (Alborn, et al, AAC 35:2282) has suggested that daptomycin acts by dissipating the voltage component of the bacterial membrane potential (DeltaY). We have examined the relationship between membrane depolarization and bactericidal activity for daptomycin. Changes in membrane potential were measured using two different fluorescent assays. Daptomycin was found to gradually (over the course of 1 hour) dissipate the membrane potential of drug treated cells in a dose-dependent manner, with loss of viability paralleling the changes in DeltaY. Flow cytometry assays revealed a broadly distributed, unimodal population, and suggested that individual cells undergo gradual dissipation. The action of daptomycin was compared to other antibacterial compounds with known modes of action. The pore-forming lantibiotic nisin was shown to rapidly (<5 minutes) dissipate DeltaY and kill Staphylococcus aureus, while the ionophores CCCP (proton) and A23187 (calcium) rapidly depolarize cells without killing, and the gyrase inhibitor ciprofloxacin kills without altering membrane potential. These data suggest that depolarization and cidal activity can be separated. We are currently focussing on understanding the mechanism by which daptomycin alters S. aureus membrane function. We have also examined the effect of daptomycin on DeltaY in a daptomycin-resistant laboratory strain and have observed subtle differences in depolarization and kill kinetics that may offer insight to the molecular basis of daptomycin resistance.
Publication Types:
Keywords:
- Anti-Bacterial Agents
- Cell Membrane
- Ciprofloxacin
- Daptomycin
- Membrane Potentials
- Membranes
- Nisin
- Staphylococcus aureus
Other ID:
UI: 102269710
From Meeting Abstracts