Solving a Novel Multidrug Resistance Puzzle: Complete Loss of Lipooligosaccharide

 描述(申请人提供)：细菌病原体利用各种分子机制在不可预测的和不利的环境条件下生存。革兰氏阴性细菌经常改变其暴露在环境中的外膜，这是一个不对称的双层，由内叶甘油磷脂和必要的外叶脂寡糖或 脂多糖。鲍曼不动杆菌是一种革兰氏阴性医院病原菌，由于其对抗生素产生耐药性的能力，在医疗保健环境中蓬勃发展。在过去的十年里，耐多药鲍曼不动杆菌已经变得广泛起来，而针对外膜必需的脂寡糖的粘菌素等最后一线抗生素，也越来越多地被开出用于治疗多药耐药感染的处方。而粘菌素耐药性是 曾经很少见的情况已经不再是这样了，特别是对鲍曼不动杆菌。独一无二的是，鲍曼不动杆菌可以完全阻断脂多糖的生物合成，从而对粘菌素和许多其他常用的抗生素产生抗药性。这一发现令人惊讶，因为脂寡糖和脂多糖以前被认为是革兰氏阴性细菌生存所必需的，但这种多药耐药机制证明它不是必需的。导致这种多药耐药表型的机制还不清楚，治疗方案也没有被探索。这项提案的总体目标是描述和理解一种新的多药耐药机制。这项建议的具体目的是(I)了解完全丧失脂低聚糖的遗传要求和(Ii)鉴定完全丧失脂低聚糖后改变的外膜通透性屏障。这项工作的完成将有助于了解革兰氏阴性菌中脂低聚糖或脂多糖的重要性，并提供对新的多药耐药机制所需的分子机制的理解。这一提议的基础科学框架也可能导致新疗法和改进疫苗的开发。

 DESCRIPTION (provided by applicant): Bacterial pathogens exploit various molecular mechanisms to survive unpredictable and adverse environmental conditions. Gram-negative bacteria often alter their environmentally exposed outer membrane, an asymmetric bilayer consisting of inner leaflet glycerophospholipids and essential outer leaflet lipooligosaccharide or lipopolysaccharide. Acinetobacter baumannii is a Gram-negative nosocomial pathogen that thrives in healthcare settings because of its ability to develop resistance to antibiotics. Multidrg resistant A. baumannii have become widespread over the past decade and last-line antibiotics such as colistin, which target the essential lipooligosaccharide in the outer membrane, have been increasingly prescribed to treat multidrug resistant infections. While colistin resistance was once rare, this is no longer the case, especially regarding A. baumannii. Uniquely, A. baumannii can completely shut down lipopolysaccharide biosynthesis to develop resistance to colistin and many other commonly prescribed antibiotics. This finding is surprising because lipooligosaccharide and lipopolysaccharide were previously thought to be required for Gram-negative bacterial viability, but this multidrug resistance mechanism proves that it is not essential. Mechanisms that contribute to this multidrug resistance phenotype are not understood and treatment options have not been explored. The overall objective of this proposal is to characterize and understand a novel multidrug resistance mechanism. The Specific Aims of this proposal are (i) to understand the genetic requirements for complete loss of lipooligosaccharide and (ii) to characterize the altered outer membrane permeability barrier after complete loss of lipooligosaccharide. Completion of this work will contribute an essential body of knowledge to the essentiality of lipooligosaccharide or lipopolysaccharide in Gram-negative bacteria and provide understanding of a molecular mechanism required for a novel multidrug resistance mechanism. The basic science framework from this proposal could also potentially lead to development of novel therapeutics and improved vaccines.