ABSTRACT
In this study, we tested five compounds belonging to a novel series of piperazine arylideneimidazolones for the ability to inhibit the AcrAB-TolC efflux pump. The biphenylmethylene derivative (BM-19) and the fluorenylmethylene derivative (BM-38) were found to possess the strongest efflux pump inhibitor (EPI) activities in the AcrAB-TolC-overproducing
Escherichia coli
strain 3-AG100, whereas BM-9, BM-27, and BM-36 had no activity at concentrations of up to 50 μM in a Nile red efflux assay. MIC microdilution assays demonstrated that BM-19 at 1/4 MIC (intrinsic MIC, 200 μM) was able to reduce the MICs of levofloxacin, oxacillin, linezolid, and clarithromycin 8-fold. BM-38 at 1/4 MIC (intrinsic MIC, 100 μM) was able to reduce only the MICs of oxacillin and linezolid (2-fold). Both compounds markedly reduced the MIC of rifampin (BM-19, 32-fold; and BM-38, 4-fold), which is suggestive of permeabilization of the outer membrane as an additional mechanism of action. Nitrocefin hydrolysis assays demonstrated that in addition to their EPI activity, both compounds were in fact weak permeabilizers of the outer membrane. Moreover, it was found that BM-19, BM-27, BM-36, and BM-38 acted as near-infrared-emitting fluorescent membrane probes, which allowed for their use in a combined influx and efflux assay and thus for tracking of the transport of an EPI across the outer membrane by an efflux pump in real time. The EPIs BM-38 and BM-19 displayed the most rapid influx of all compounds, whereas BM-27, which did not act as an EPI, showed the slowest influx.
摘要
在本研究中,我们测试了属于新型哌嗪芳基亚咪唑酮系列的五个化合物对 AcrAB-TolC 外排泵的抑制能力。结果发现,联苯亚甲基衍生物(BM-19)和芴亚甲基衍生物(BM-38)在产生 AcrAB-TolC 的大肠杆菌中具有最强的外排泵抑制剂(EPI)活性。
大肠杆菌
菌株 3-AG100 中具有最强的外排泵抑制剂(EPI)活性,而 BM-9、BM-27 和 BM-36 在尼罗河红外排试验中浓度高达 50 μM 时没有活性。MIC 微稀释试验表明,1/4 MIC(固有 MIC,200 μM)的 BM-19 能将左氧氟沙星、氧西林、利奈唑胺和克拉霉素的 MIC 降低 8 倍。BM-38 的 MIC 值为 1/4(固有 MIC 值为 100 μM),但只能将奥沙西林和利奈唑胺的 MIC 值降低 2 倍。这两种化合物都显著降低了利福平的 MIC(BM-19,32 倍;BM-38,4 倍),这表明外膜渗透是另一种作用机制。硝基蝶呤水解试验表明,除了 EPI 活性外,这两种化合物实际上还具有弱的外膜渗透作用。此外,研究还发现 BM-19、BM-27、BM-36 和 BM-38 可作为近红外发射荧光膜探针,因此可将它们用于流入和流出联合检测,从而实时跟踪外排泵通过外膜转运 EPI 的情况。在所有化合物中,EPI BM-38 和 BM-19 的流入速度最快,而不作为 EPI 的 BM-27 的流入速度最慢。