Exploiting Riboswitch Sensors to Reveal Antibiotics Uptake and Retention in Gram Negative Bacteria

摘要 耐多药铜绿假单胞菌和其他革兰阴性杆菌感染挑战临床医生 为了找到安全有效的抗生素方案，从虚弱的人群中根除这些机会性病原体， 通常是他们攻击的免疫系统受损的宿主。铜绿假单胞菌细胞膜的两个特征--它的局限性 对小分子的渗透性以及大量的结构性和诱导性外排系统 包含-使这种病原体对许多可用的抗菌剂产生内在抗药性，并有助于 对现有的少量抗假单胞菌抗生素产生了获得性耐药性。这严重限制了 使用全细胞分析识别抗生素活性的能力--作为穿透和可以 抑制关键代谢途径通常在可测量地抑制细菌生长或 生存能力。鉴定关键细菌酶的新型小分子抑制剂的方法通常在以下情况下失败 这些小分子不能达到有效的细菌内浓度--我们对 可悲的是，允许渗透和保留的化学物质是不完整的。 在这一应用中，我们使用了一系列不同的核糖开关，敏感和特异的基于RNA的小分子 传感器，作为细菌生理受到干扰的快速和定量指标。通过多路传输 几种核糖开关，报告了丙二醛ztp和ppGpp以及有毒产品的积累 在SAM利用率增加的情况下，SAH，我们可以有效地筛选细菌对亚 小分子的麦克风水平。我们的方法将这些核糖开关记者置于同基因的MDR和外排- 缺乏铜绿假单胞菌的菌株，同时产生物理和结构化学信息 允许穿透和外流避免并识别可被开发为 新抗菌剂的线索。我们的药物化学方法将建立在这两种知识的基础上， 使新的抗假单胞化合物能够被识别和优化。

ABSTRACT Infections caused by MDR Pseudomonas aeruginosa and other Gram-negative pathogens challenge clinicians to find safe and effective antibiotic regimens that can eradicate these opportunistic pathogens from the frail, often immunocompromised hosts that they target. Two features of the P. aeruginosa cell envelope - its limited permeability to small molecules and the large number of both constitutive and inducible efflux systems it contains - render this pathogen intrinsically resistant to many available antimicrobials and contribute to acquired resistance toward the small set of existing anti-Pseudomonal antibiotics. This seriously limits the ability to identify “hits” with antibiotic activity using whole-cell assays - as compounds that penetrate and can inhibit key metabolic pathways are often effluxed out before they measurably inhibit bacterial growth or viability. Approaches that identify novel small molecule inhibitors of key bacterial enzymes often fail when these small molecules cannot achieve effective intrabacterial concentrations - and our understanding of the chemistries that would allow for penetration and retention is woefully incomplete. In this application we use a diverse array of riboswitches, sensitive and specific RNA-based small molecule sensors, as rapid and quantitative indicators that bacterial physiology has been perturbed. By multiplexing several riboswitches that report on accumulation of the alarmones ZTP and ppGpp, as well as the toxic product of increased SAM utilization, SAH, we can effectively screen for “signatures” of a bacterial response to sub- MIC levels of small molecules. Our approach places these riboswitch reporters in isogenic MDR and efflux- deficient P. aeruginosa strains, simultaneously yielding information about both physical and structural chemical features that allow penetration and efflux-avoidance and identifying “hit” molecules that can be developed as leads for new antibacterial agents. Our medicinal chemistry approach will build on both types of knowledge, allowing novel anti-Pseudomonal compounds to be identified and optimized.