Resistance to Carbapenem Antibiotics in Acinetobacter baumannii

摘要 鲍曼不动杆菌被美国疾病控制与预防中心列为一种临床病原菌，它会产生严重的抗生素。 在美国的抵抗威胁。鲍曼不动杆菌对不同的抗菌剂具有抗药性。 类，但最麻烦的是对最后手段的碳青霉烯类抗生素的耐药性，这是 治疗这种微生物引起的感染的首选药物。其主要作用机制是 鲍曼不动杆菌对碳青霉烯类抗生素的耐药性是产生抗生素失活酶， 碳青霉烯-D类β-内酰胺酶或CHDLS。此外，对碳青霉烯类药物的敏感性 目标，细菌青霉素结合蛋白(PBPs)，抗生素对细菌细胞的渗透率 和/或它们被外排泵排出也会造成阻力。对以下病毒的抗药性水平 碳青霉烯类抗生素在世界一些地区高达90%，感染死亡率 由这类细菌引起的死亡率高得惊人，高达50%。我们的长期目标是开发小说 治疗致命鲍曼不动杆菌感染的抗生素。在这笔赠款的第一个资金周期内 我们对临床上重要的CHDLS进行了深入的表征，并提出了 研究了其碳青霉烯酶的活性机制，为开发新的碳青霉烯酶提供了指导 能抑制这些酶的碳青霉烯类抗生素的产生。这项研究的继续将 与John Buynak博士(合作者)合作，他开发了数十种非典型的- 改良的碳青霉烯类抗生素。我们用这些抗生素来测试我们提出的治疗机制 发现三种抑制最普遍的鲍曼不动杆菌CHDL，OXA-23，并拥有 (与商用碳青霉烯相比)对产生OXA-23的A. 鲍曼尼。我们提出的研究旨在深入刻画这些有前途的小说 毒品。我们将测定我们的化合物对鲍曼不动杆菌的活性。 并揭示其抑制这些酶的能力的动力学和结构特征 (目标1)。我们将评估我们的新型碳青霉烯与它们的靶标多溴联苯并确定 外排泵和孔道蛋白在多大程度上影响细菌对这些抗生素的耐药性(目标2)。 最后，我们将设计和表征数十种新型碳青霉烯类抗生素，目的是 通过增强其对CHDLS的抑制效力，进一步提高其抗菌活性， 提高多溴联苯的亲和力，增加渗透率和外排阻力(目标3)。

ABSTRACT Acinetobacter baumannii is listed by the CDC as a clinical pathogen that poses a serious antibiotic resistance threat in the United States. A. baumannii is resistant to antimicrobial agents of different classes, but the most troublesome is resistance to the last resort carbapenem antibiotics, which were the drugs of choice for treatment of infections caused by this microorganism. The major mechanism of resistance of A. baumannii to carbapenems is production of antibiotic-inactivating enzymes, carbapenem-hydrolyzing class D β-lactamases or CHDLs. In addition, sensitivity of carbapenem targets, bacterial penicillin-binding proteins (PBPs), rates of antibiotic penetration into the bacterial cell and/or their expulsion by efflux pumps can also contribute to resistance. Levels of resistance to carbapenem antibiotics reach up to 90% in some parts of the world, and mortality rates from infections caused by such bacteria are staggeringly high, up to 50%. Our long-term goal is to develop novel antibiotics for treatment of deadly A. baumannii infections. During the first cycle of funding for this grant proposal, we performed in-depth characterization of clinically important CHDLs and proposed the mechanism for their carbapenemase activity, which provides guidance for development of a new generation of carbapenems capable of inhibiting these enzymes. The continuation of this research will be a collaborative effort with Dr. John Buynak (co-PI) who developed dozens of novel atypically- modified carbapenem antibiotics. We used these antibiotics to test our proposed mechanism for deacylation and found three that inhibit the most prevalent A. baumannii CHDL, OXA-23, and possess superior activity (when compared to commercial carbapenems) against OXA-23-producing A. baumannii. Our proposed studies are aimed at in-depth characterization of these promising novel drugs. We will determine activity of our compounds against A. baumannii strains expressing major CHDLs and unveil kinetic and structural features responsible for their ability to inhibit these enzymes (Aim 1). We will evaluate interaction of our novel carbapenems with their targets, PBPs, and determine to what extent efflux pumps and porins influence bacterial resistance to these antibiotics (Aim 2). Finally, we will design and characterize several dozen novel carbapenem antibiotics with the aim to further improve their antimicrobial activity by enhancing their inhibitory potency against CHDLs, improving affinity for PBPs and increasing penetration rates and resistance to efflux (Aim 3).