Solving a Multidrug Resistance Puzzle: Complete Loss of Lipooligosaccharide

项目摘要/摘要 细菌病原体利用各种分子机制在恶劣的环境条件下生存。 革兰氏阴性菌对其外膜进行修饰，外膜是由内叶组成的不对称双层 甘油磷脂和必需的外叶脂寡糖或脂多糖。不动杆菌 鲍曼氏杆菌是一种革兰氏阴性医院病原菌，由于其能够在医疗保健环境中蓬勃发展，它能够 对抗生素产生抗药性。过去，耐多药鲍曼不动杆菌已变得普遍存在。 十年和最后一线抗生素，如粘菌素，它针对的是脂寡糖的脂A结构域 外膜，越来越多地被开出用于治疗感染的处方。虽然粘菌素耐药性一度很少见， 鲍曼不动杆菌形成了一种独特的抗性机制。鲍曼不动杆菌能完全阻断A类脂质 生物合成对包括粘菌素在内的许多处方药产生多重抗药性。这一发现是 令人惊讶的是，内毒素被认为是革兰氏阴性菌生存所必需的，但这一点 机制证明并非如此。导致这种多药耐药表型的分子因素不是 了解和治疗方案还没有被探索。 这项建议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)表征外膜蛋白， 支持鲍曼氏乳杆菌的存活和(Ii)BaeSR双组分系统的表征及其 监管产品。这些目标的实现将推动我们的知识体系理解 革兰氏阴性细菌中脂质A的重要性，并提供了对所需分子机制的理解 一种新的多药耐药机制。此外，这项提案的发现还可能 导致开发新的疗法和改进的疫苗。

Project Summary/Abstract Bacterial pathogens exploit various molecular mechanisms to survive adverse environmental conditions. Gram-negative bacteria modify their outer membrane, which is 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. Multidrug resistant A. baumannii have become widespread over the past decade and last-line antibiotics such as colistin, which targets the lipid A domain of lipooligosaccharide in the outer membrane, has been increasingly prescribed to treat infections. While colistin resistance was once rare, A. baumannii has developed a unique resistance mechanism. A. baumannii can completely shut down lipid A biosynthesis to develop multidrug resistance to many prescribed antibiotics, including colistin. This finding is surprising because lipopolysaccharide was thought to be required for Gram-negative viability, but this mechanism proves otherwise. Molecular factors 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 to (i) Characterize the outer membrane proteins that support LOS- A. baumannii survival and (ii) characterization of the BaeSR two-component system and its regulatory products. Completion of these AIMS will advance our body of knowledge to understand the essentiality of lipid A in Gram-negative bacteria and provide understanding of a molecular mechanism required for a novel multidrug resistance mechanism. Furthermore, the findings from this proposal could also potentially lead to development of novel therapeutics and improved vaccines.