Mechanisms of Resistance in Gram-Negative Bacteria

患有囊性纤维化（CF）的患者发展为慢性气道感染， 机会性革兰氏阴性菌铜绿假单胞菌气道炎症 和无细菌破坏的嗜酸性浸润是这些感染的特征。它 已经显示从囊性纤维化患者分离的假单胞菌具有特异性， 脂质A结构中的毒性相关修饰。这些修改， 包括用棕榈酸酯和4-氨基阿拉伯糖取代 阳离子抗菌肽（CAMPs），先天免疫的重要组成部分， 和多粘菌素，一种CAMP抗生素。负责4-羟色胺生物合成的酶 氨基阿拉伯糖-脂质A聚集在最近重新命名为ArnBCADTEF的操纵子中。 这些基因中的任何一个的突变都消除了4-氨基阿拉伯糖添加到脂质A中， 对CAMP的抵抗。基于我们之前对ArnA的结构和生物化学工作 我们已经开发了选择性抑制ArnA的策略。在这份提案中，我们还 目标ArnD，一种假设的脱甲酰基酶，对4- 氨基阿拉伯糖-脂质A，用于生物化学和结构表征。抑制任何 这些酶将消除铜绿假单胞菌对抗菌剂的耐药性 肽，因此大大增强了宿主对慢性 感染假单胞菌。为了提高生活质量和生存年龄， CF患者，至关重要的是，制定新的策略来管理他们的肺 感染.鉴于这些感染的慢性性质， 阻力是一个根本问题。本提案侧重于以下方面的特征： 介导对CAMPs的抗性的细菌靶标。

Patients with Cystic Fibrosis (CF) develop chronic airway infections with the opportunistic gram negative bacteria Pseudomonas aeruginosa. Airway inflammation and neutrophilic infiltration without bacterial destruction characterize these infections. It has been shown that Pseudomonas isolated from Cystic Fibrosis patients have specific, virulence-associated modifications in their lipid A structure. These modifications, which include substitutions with palmitate and 4-aminoarabinose, are responsible for resistance to cationic antimicrobial peptides (CAMPs), an important component of innate immunity and Polymyxin, a CAMP antibiotic. The enzymes responsible for the biosynthesis of 4- aminoarabinose-lipid A are clustered in an operon recently renamed to ArnBCADTEF. Mutation of any of these genes abolishes 4-aminoarabinose addition to lipid A and resistance to CAMPs. Based on our previous structural and biochemical work with ArnA we have developed a strategy for selective inhibition ArnA . In this proposal we also target ArnD, a hypothetical deformylase essential for the biosynthesis of 4- aminoarabinose-lipid A, for biochemical and structural characterization. Inhibition of any of these enzymes would abolish Pseudomonas aeruginosa resistance to antimicrobial peptides, therefore greatly enhancing the host immune response against chronic infections with Pseudomonas. To improve both the quality of life and the survival age of CF patients it is crucial that new strategies are developed to manage their pulmonary infections. Given the chronic nature of these infections preventing or abolishing resistance is a fundamental problem. This proposal focuses on the characterization of bacterial targets that mediate resistance to CAMPs.