Infiltrating MDR Gram-negative bacteria using an innovative antibiotic-assisted translocation approach

“耐药感染已经导致全球每年有相当数量的死亡。其中，由肠杆菌科、不动杆菌、假单胞菌和克雷伯氏菌等耐多药革兰氏阴性病原体引起的疾病是最严重的健康威胁。一般来说，革兰氏阴性细菌对大量抗生素具有内在抗药性，并可能导致难以治疗的感染。一个主要缺点是实现全细胞活性，这一缺点阻碍了几乎所有具有抗革兰氏阴性细菌活性的新类别的进展。革兰氏阴性菌具有内置的防御机制，包括不易被药物和/或抗生素穿透的细胞内外膜，以及多个细胞表面排出泵，这些泵可以在细胞有机会杀死细菌之前将设法穿过细胞膜的药物排出细胞外。增强现有或新抗生素对耐多药革兰氏阴性病原体的抗菌活性将为这些原本有效和有益的抗生素提供相当大的价值。因此，需要一种策略来克服细菌的防御机制，使这些抗生素具有持续的治疗效果，本项目旨在提供一种方法，通过它绕过耐药革兰氏阴性病原体的这些细菌防御机制。一种基于非铁载体的创新方法被发现，以介导抗菌剂快速促进输送到细菌的细胞质，从而绕过外膜和外排机制(S)。它采用了一种基本的、非冗余的摄取途径，该途径在革兰氏阴性菌(和革兰氏阳性菌)中高度保守和结构性表达，并对细菌生长和生存所必需的特定碳水化合物具有高度选择性。该项目旨在证明，这种抗生素辅助的易位平台技术与针对两个新的但经过验证的细菌靶点的药物的组合，将提供一个有效的解决方案，显著降低使用这些新型抑制剂抑制多种类型的MDR细菌生长所需的剂量和MIC(最低抑菌浓度)。这两个新的但有效的细菌靶点由于细菌防御机制导致的整体细胞活性低下而被终止。这些靶标包括LPxC，负责类脂A生物合成的第一步的酶，类脂A是外膜的关键成分，以及MurC，参与肽聚糖生物合成的四种氨基酸添加酶中的第一种。

"Drug-resistant infections are already responsible for a significant number of deaths globally each year. Of these, those caused by MDR Gram-negative pathogens such as Enterobacteriaceae, Acinetobacter, Pseudomonas and _Klebsiella_ are amongst the most serious health threats. Gram-negative bacteria, in general, are intrinsically resistant to a significant number of antibiotics and can cause infections that are difficult to treat. A major drawback that has stalled progress on nearly all new classes with potential for activity against Gram-negative bacteria has been achieving whole-cell activity. Gram-negative bacteria have built-in defence mechanisms, including an outer and inner cell membrane that is not easily penetrated by drugs and/or antibiotics, and multiple cell-surface efflux pumps that can expel drugs that do manage to cross the cell membrane, out of the cell before it has the chance to kill the bacteria.Enhancing the antibacterial activity of current or new antibiotics against MDR Gram-negative pathogens would provide considerable value to these otherwise effective and beneficial antibiotics. Therefore there exists a need for strategies which will overcome the defence mechanisms of bacteria to allow these antibiotics to have a sustained therapeutic effect and the present project aims to provide a means by which to bypass these bacterial defence mechanisms in MDR Gram-negative pathogens.An innovative non-siderophore-based approach to mediate fast facilitated delivery of an antibacterial agent into the cytoplasm of bacteria, thereby bypassing the outer membrane and efflux mechanism(s) has been discovered. It employs an essential and non-redundant uptake pathway that is highly conserved and constitutively expressed across Gram-negative bacteria (and Gram-positive) and is highly selective for a specific carbohydrate that is essential for bacterial growth and survival. Selective enzymatic cleavage within the cytoplasm results in the release of the active anti-bacterial agent.The project will aim to demonstrate that combinations of this antibiotic-assisted translocation platform technology with drugs against two novel but validated bacterial targets that have been terminated due to poor whole-cell activity caused by bacterial defence mechanisms, will provide an effective solution in significantly lowering the dose and MIC (minimum inhibitory concentration) that is required to inhibit bacterial growth of multiple types of MDR bacteria with these novel inhibitors. These targets include LPxC, the enzyme responsible for the first committed step in the biosynthesis of lipid A, a key component of the outer membrane, as well as MurC, the first of four amino-acid adding enzymes involved in the biosynthesis of the peptidoglycan,"