Direct Electric Current Treatment under Physiologic Saline Conditions Kills Staphylococcus epidermidis Biofilms via Electrolytic Generation of Hypochlorous Acid
Direct Electric Current Treatment under Physiologic Saline Conditions Kills Staphylococcus epidermidis Biofilms via Electrolytic Generation of Hypochlorous Acid
复制标题
DOI：
10.1371/journal.pone.0055118
复制
发表时间：
2013-02-04
期刊：
影响因子：
3.7
通讯作者：
Stewart, Philip S.
中科院分区：
文献类型：
--
作者：
Sandvik, Elizabeth L.;McLeod, Bruce R.;Stewart, Philip S.
本研究的目的是研究直流电降低表皮葡萄球菌生物膜与环丙沙星在生理盐水条件下的活力的机制，该生理盐水条件旨在接近受感染的人工关节中的条件。在CDC生物膜反应器中生长的生物膜在含有9 g/L总NaCl的1/10强度胰蛋白酶大豆肉汤中暴露于电流24小时。在存在和不存在环丙沙星的情况下，在所有四个水平（0.7至1.8 mA/cm（2））下应用直流电，观察到剂量依赖性对数减少高达6.7 log（10）CFU/cm（2）。在相同的电流水平下，与未加环丙沙星的孔相比，加环丙沙星的威尔斯孔的对数减少值无显著差异。当当前的曝光重复没有生物膜或有机物在介质中，显着产生的游离氯进行测量。相当于每个电流水平的24小时终点浓度的游离氯剂量显示出模拟通过电流应用实现的杀灭。电流暴露（1.8 mA/cm（2））在缺乏氯化物的介质中，并以硫酸盐、硝酸盐或磷酸盐作为替代电解质进行修正，分别产生3、2和0 log减少的减少杀灭。直流电也杀死铜绿假单胞菌生物膜时，NaCl的存在。这些结果一起表明，从氯化物产生次氯酸的电解反应可能是直流电应用功效的主要贡献者。因此，如果要研究直流电在体内的医学应用，生理相关的NaCl浓度是实验设计中的关键参数。
The purpose of this study was to investigate the mechanism by which a direct electrical current reduced the viability of Staphylococcus epidermidis biofilms in conjunction with ciprofloxacin at physiologic saline conditions meant to approximate those in an infected artificial joint. Biofilms grown in CDC biofilm reactors were exposed to current for 24 hours in 1/10th strength tryptic soy broth containing 9 g/L total NaCl. Dose-dependent log reductions up to 6.7 log(10) CFU/cm(2) were observed with the application of direct current at all four levels (0.7 to 1.8 mA/cm(2)) both in the presence and absence of ciprofloxacin. There were no significant differences in log reductions for wells with ciprofloxacin compared to those without at the same current levels. When current exposures were repeated without biofilm or organics in the medium, significant generation of free chlorine was measured. Free chlorine doses equivalent to the 24 hour endpoint concentration for each current level were shown to mimic killing achieved by current application. Current exposure (1.8 mA/cm(2)) in medium lacking chloride and amended with sulfate, nitrate, or phosphate as alternative electrolytes produced diminished kills of 3, 2, and 0 log reduction, respectively. Direct current also killed Pseudomonas aeruginosa biofilms when NaCl was present. Together these results indicate that electrolysis reactions generating hypochlorous acid from chloride are likely a main contributor to the efficacy of direct current application. A physiologically relevant NaCl concentration is thus a critical parameter in experimental design if direct current is to be investigated for in vivo medical applications.