Carbapenemase-Stable Carbapenem Antibiotics for Treatment of Multidrug-Resistant Acinetobacter baumannii Infections

鲍曼不动杆菌被CDC列为临床病原体，具有严重的抗生素耐药性 在美国的威胁，由于其耐药性的最后手段碳青霉烯类抗生素（碳青霉烯耐药 A.鲍曼不动杆菌或CRAb），它们是治疗由这种微生物引起的感染的首选药物。 此外，CRAb通常对不同类别的抗菌剂具有抗性（多药耐药A.鲍曼不 或MDRAb），这严重限制了可用的治疗选择。主要的抗性机制是： 鲍曼不动杆菌对碳青霉烯类抗生素的敏感性主要是产生碳青霉烯类抗生素失活酶、碳青霉烯类水解酶D β- 内酰胺酶或CHDL。此外，A类和B类碳青霉烯酶、碳青霉烯类靶点敏感性 （细菌青霉素结合蛋白或PBP）、抗生素渗透到细菌细胞中的速率及其 通过外排泵的排出也可导致抗性。对碳青霉烯类抗生素的耐药水平高达 在世界某些地区高达90%，由这种细菌引起的感染的死亡率令人震惊。 高，高达50%。我们的长期目标是开发新的抗生素来治疗致命的MDRAb感染。 在过去的十年中，Vakulenko小组对临床上重要的 CHDLs，为开发能够抑制CHDLs的新一代碳青霉烯类提供指导 这些酶。与此同时，John Buynak博士（共同PI）的研究小组开发了数十种新的药物修饰 碳青霉烯类抗生素。我们评估了这些抗生素对MDRAb的活性，并证明， 它们中的三种具有上级的抗MDRAb活性（当与商业碳青霉烯类相比时）。所有三 抑制了最普遍的A.鲍曼不动杆菌CHDL，OXA-23，并具有不同的抑制活性谱， 其他CHDL和其他类别的碳青霉烯酶。其中一种化合物具有前所未有的宽 活性谱，并抵抗各种临床上重要的碳青霉烯酶的水解 分子分类在这份资助申请中，我们建议对我们的小说进行详细的描述。 碳青霉烯类抗生素。我们将测定我们的化合物对A的活性。鲍曼不动杆菌菌株表达 主要CHDL和其他碳青霉烯酶，并揭示了负责其能力的动力学和结构特征 抑制这些酶（目的1）。我们将研究我们的新型碳青霉烯类与其靶点PBPs的相互作用， 并确定外排泵和孔蛋白在多大程度上影响细菌对这些抗生素的耐药性（目的2）。 我们将设计和表征几十种新型碳青霉烯类抗生素，以进一步提高其抗菌活性。 通过增强其对各种碳青霉烯酶的抑制效力，改善对PBP的亲和力， 增加渗透率和外排阻力（目标3）。我们将对我们最好的 新的碳青霉烯类，以评估其溶解度、稳定性和毒性。最后，我们最好的化合物将被评估 在动物研究中评价它们作为抗MDRAb的新型治疗剂的潜力（目的4）。

Acinetobacter baumannii is listed by the CDC as a clinical pathogen that poses a serious antibiotic resistance threat in the United States, due to its resistance to the last resort carbapenem antibiotics (carbapenem-resistant A. baumannii or CRAb), which were the drugs of choice for treatment of infections caused by this microorganism. In addition, CRAb is often resistant to antimicrobial agents of different classes (multi-drug-resistant A. baumannii or MDRAb), which severely limits available therapeutic options. 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, carbapenemases of classes A and B, sensitivity of carbapenem targets (bacterial penicillin-binding proteins or PBPs), rates of antibiotic penetration into the bacterial cell and their expulsion by efflux pumps can also contribute to resistance. Levels of resistance to carbapenems 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 MDRAb infections. Over the last decade, the Vakulenko group has performed in-depth characterization of clinically important CHDLs, which provides guidance for development of a new generation of carbapenems capable of inhibiting these enzymes. Concurrently, Dr. John Buynak’s (co-PI) group developed dozens of novel atypically-modified carbapenem antibiotics. We evaluated these antibiotics for their activity against MDRAb and demonstrated that three of them possess superior activity (when compared to commercial carbapenems) against MDRAb. All three inhibited the most prevalent A. baumannii CHDL, OXA-23, and had varying spectra of inhibitory activity against other CHDLs and carbapenemases of other classes. One of these compounds had an unprecedented wide spectrum of activity and resisted hydrolysis by a wide range of clinically important carbapenemases of all molecular classes. In this grant application, we propose to perform detailed characterization of our novel carbapenem antibiotics. We will determine activity of our compounds against A. baumannii strains expressing major CHDLs and other carbapenemases and unveil kinetic and structural features responsible for their ability to inhibit these enzymes (Aim 1). We will study 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). We will design and characterize several dozen novel carbapenem antibiotics to further improve their antimicrobial activity by enhancing their inhibitory potency against various carbapenemases, improving affinity for PBPs and increasing penetration rates and resistance to efflux (Aim 3). We will perform in vitro characterization of our best novel carbapenems to assess their solubility, stability and toxicity. Finally, our best compounds will be evaluated in animal studies to appreciate their potential as novel therapeutic agents against MDRAb (Aim 4).