Compound Uptake into E. coli Can Be Facilitated by N‑Alkyl Guanidiniums and Pyridiniums

Multidrug-resistant Gram-negative bacterial infections are on the rise, and with no FDA approvals for new classes of broad-spectrum antibiotics in over 50 years, these infections constitute a major threat to human health. A significant challenge is the inability of most compounds to accumulate in Gram-negative bacteria. Recently developed predictive guidelines show that appending a primary amine to an appropriately shaped compound can enhance Gram-negative accumulation. Here, we report that other positively charged nitrogen functional groups, namely, N-alkyl guanidiniums and pyridiniums, can also facilitate compound uptake into Gram-negative bacteria. The accumulation of a set of 60 nonantibiotic compounds, consisting of 20 primary amines and their corresponding guanidiniums and pyridiniums, was assessed in Escherichia coli. We also installed these alternate functional groups onto antibiotic scaffolds and assessed their accumulation and antibacterial activity in Gram-negative bacteria. The results suggest that other positively-charged, nitrogen-containing functional groups should be considered when designing antibiotics with Gram-negative activity.多重耐药革兰氏阴性细菌（Gram-negative bacteria）感染呈逐年上升趋势，且过去五十余年来未有新型广谱抗生素类别获得美国食品药品监督管理局（Food and Drug Administration, FDA）批准，此类感染已对人类健康构成重大威胁。当前一项核心挑战在于，绝大多数化合物无法在革兰氏阴性菌体内有效蓄积。近期提出的预测性研究指南表明，在结构适配的化合物上引入伯胺基团，可提升其在革兰氏阴性菌体内的蓄积能力。本研究发现，其他带正电的含氮官能团——即N-烷基胍基（N-alkyl guanidiniums）与吡啶鎓基团（pyridiniums）——同样可促进化合物被革兰氏阴性菌摄取。本研究以大肠杆菌（Escherichia coli）为模型，对包含20种伯胺及其对应胍基、吡啶鎓修饰衍生物的60种非抗生素类化合物的蓄积情况进行了评估；此外，本研究还将上述替代官能团引入抗生素母核骨架，并评估了其在革兰氏阴性菌体内的蓄积能力与抗菌活性。研究结果提示，在设计具备革兰氏阴性菌抗菌活性的抗生素时，应考虑采用其他带正电的含氮官能团。