Consequences of daptomycin-mediated membrane damage in Staphylococcus aureus
Consequences of daptomycin-mediated membrane damage in Staphylococcus aureus
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DOI：
10.1093/jac/dkn321
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发表时间：
2008-11-01
影响因子：
5.2
通讯作者：
Chopra, Ian
中科院分区：
文献类型：
--
作者：
Hobbs, Joanne Karen;Miller, Keith;Chopra, Ian
目的：达托霉素对金黄色葡萄球菌的致死作用是由于 K+ 丢失和膜去极化所致。然而，这些事件是否单独导致细胞死亡一直受到质疑。我们试图确定达托霉素介导的膜损伤的其他后果是否可能导致细胞死亡。方法：使用先前建立的测定法来评估达托霉素在 10 分钟的单一时间点的膜损伤活性。还进行了更详细的时程实验以确定膜去极化以及 K+、Mg2+ 和 ATP 渗漏的动力学。还通过测定放射性前体与大分子的结合来确定接触达托霉素后大分子合成的抑制动力学。结果：在接触抗生素10分钟后的单时间点测定中，达托霉素没有表现出膜损伤活性。动力学分析证实了这些结果，因为细胞内成分的渗漏直到 20-30 分钟才发生，膜去极化是逐渐的，细胞在接触达托霉素后至少 30 分钟仍保持生物合成活性。接触达托霉素后活力迅速下降，并且似乎先于其他可检测到的变化。结论：这些数据表明，达托霉素诱导的 Mg2+ 和 ATP 损失与先前报道的 K+ 渗漏和膜去极化同时发生。我们认为达托霉素的致死活性不仅仅是由于 K+ 的损失，而且可能涉及更普遍的膜损伤。
Objectives: The proposed lethal action of daptomycin on Staphylococcus aureus results from the loss of K+ and membrane depolarization. However, whether these events alone cause cell death has been questioned. We sought to determine whether other consequences of daptomycin-mediated membrane damage may contribute to cell death.Methods: Previously established assays were used to evaluate the membrane damaging activity of daptomycin at a single time-point of 10 min. More detailed time-course experiments were also performed to determine the kinetics of membrane depolarization and leakage of K+, Mg2+ and ATP. The kinetics of inhibition of macromolecular synthesis following exposure to daptomycin were also determined by assaying the incorporation of radioactive precursors into macromolecules.Results: Daptomycin exhibited no membrane damaging activity in single time-point assays following exposure to the antibiotic for 10 min. Kinetic analysis confirmed these results as leakage of intracellular components did not occur until 20-30 min, membrane depolarization was gradual and cells remained biosynthetically active for at least 30 min after exposure to daptomycin. Viability declined rapidly after exposure to daptomycin and appeared to precede other detectable changes.Conclusions: These data show that daptomycin-induced loss of Mg2+ and ATP occurs in conjunction with the previously reported leakage of K+ and membrane depolarization. We propose that the lethal activity of daptomycin is not simply due to loss of K+ and probably involves more general damage to the membrane.