Daptomycin exerts rapid bactericidal activity against Bacillus anthracis without disrupting membrane integrity |
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Authors: | Yu-hua XING Wei WANG Su-qin DAI Ti-yan LIU Jun-jie TAN Guo-Iong QU Yu-xia LI Yan LING Gang LIU Xue-qi FU Hui-peng CHEN |
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Institution: | [1]Beijing Institute of Biotechnology, Beijing 100071, China [2]College of Life Science, Jilin University, Changchun 130012, China |
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Abstract: | Aim:To examine whether the novel cyclic lipopeptide antibiotic daptomycin could be used to treat anthrax and to study the mechanisms underlying its bactericidal action against Bacillus anthracis.Methods:Spore-forming B anthracis AP422 was tested. MIC values of antibiotics were determined. Cell membrane potential was measured using flow cytometric assays with membrane potential-sensitive fluorescent dyes. Cell membrane integrity was detected using To-Pro-3 iodide staining and transmission electron microscopy. K+ efflux and Na+ influx were measured using the fluorescent probes PBFI and SBFI-AM, respectively.Results:Daptomycin exhibited rapid bactericidal activity against vegetative B anthracis with a MIC value of 0.78 μg/mL, which was comparable to those of ciprofloxacin and penicillin G. Furthermore, daptomycin prevented the germinated spores from growing into vegetative bacteria. Daptomycin concentration-dependently dissipated the membrane potential of B anthracis and caused K+ efflux and Na+ influx without disrupting membrane integrity. In contrast, both ciprofloxacin and penicillin G did not change the membrane potential of vegetative bacteria or spores. Penicillin G disrupted membrane integrity of B anthracis, whereas ciprofloxacin had no such effect.Conclusion:Daptomycin exerts rapid bactericidal action against B anthracis via reducing membrane potential without disrupting membrane integrity. This antibiotic can be used as an alternate therapy for B anthracis infections. |
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Keywords: | Keywords: anthrax Bacillus anthracis antibiotic daptomycin ciprofloxacin penicillin CCCP nisin valinomycin membrane potential membrane integrity |
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