Determining the value of PBP 7/8 as an antimicrobial target for XDR-A. baumannnii

对退伍军人医疗保健的预期影响。高耐药性导致的感染发生率 鲍曼不动杆菌不断增加。真正的泛耐药（PDR）菌株已有报道。 不幸的是，新批准的抗菌药物头孢他嗪-他唑巴坦、头孢他啶-阿维巴坦和 美罗培南/vaborbactam 对耐药鲍曼不动杆菌的活性较差。需要识别新的 对抗鲍曼不动杆菌的抗菌药物迫在眉睫。 背景。我们已经证明鲍曼不动杆菌低分子质量 (LMM) 青霉素结合 蛋白 7/8 (PBP 7/8) 在大鼠肺炎和大鼠体内是必需的（即宿主细菌存活所需） 皮下脓肿感染模型，并且是在人血清和腹水中存活所必需的。我们最初的 对 PBP 7/8 的研究是在抗菌敏感菌株 AB307-0294 中进行的。这些发现有 自从被广泛耐药（XDR）菌株 HUMC1 证实以来。自从我们最初观察以来 其他研究人员使用 INseq 和 Tn-seq 表明，鲍曼不动杆菌在 分别建立大蜡螟昆虫感染模型和血清。 PBP 7/8 具有许多特性， 支持其作为高价值药物靶点的潜力。然而，基于丰富的实验室培养基的研究，LMM 包括 PBP 7/8 在内的 PBP 被认为是非必需的。因此，PBP 7/8 收到的信息很少 作为抗菌靶标受到关注，但尚未考虑用于鲍曼不动杆菌。然而，我们的数据 与这一范式相矛盾，并支持需要对 XDR 鲍曼不动杆菌中的 PBP 7/8 进行额外研究。 因此，我们的目标是验证 PBP 7/8 作为药物靶点，描述介导其前体的机制。 体内和体内重要性，并鉴定使 PBP 7/8 失活的化合物。 目标和方法。为了实现这些目标，PBP 7/8 的研究将扩大到包括 鲍曼不动杆菌的其他 XDR 菌株以证实我们的发现具有普遍性（目标 1）。目标1也将 探索 PBP 7/8 使鲍曼不动杆菌离体和体内生长/存活的机制，以及 确定其防御的先天宿主防御因素。越来越多的数据支持治疗感染的必要性 由于 XDR 分离物具有多种药物，从而提高功效并防止发展 的阻力。我们证明 PBP 7/8 产量的损失会增加补体的敏感性 溶菌酶介导的杀菌活性和改变细胞结构支持以下假设： 无法产生 PBP 7/8 会影响渗透性，这是 A. 固有抗菌素耐药性的一个关键因素。 鲍曼氏菌。因此，该提案的另一个目标是评估 PBP 7/8 的损失是否 生产增强了抗菌药物和/或单克隆抗体辅助治疗的活性 直接针对胶囊（目标 2）。目标 2 中的其他研究将评估 PBP 7/8 的缺失是否会影响 其他 PBP 和 ampC 表达的产生。这些数据将产生额外的机制见解 无法产生 PBP 7/8 的后果。最后，目标 3 将开始识别过程 一种对 PBP 7/8 有活性的“工具”化合物。将针对活的野生型 XDR 菌株进行筛选 化学库来鉴定具有杀菌活性的针对 PBP 7/8 的化合物。附加 正交测定将建立特异性，确定其质量，并优先考虑已识别的抑制剂 下游优化和临床前研究。该提案的可交付成果将验证该范例 转变 PBP 7/8 作为抗菌靶点的价值，并为开发 针对这种 XDR 病原体的新型抗菌剂。

Anticipated Impacts on Veterans Health Care. The incidence of infections due to highly resistant Acinetobacter baumannii is increasing. True pan drug resistant (PDR) strains have been reported. Unfortunately, the newly approved antimicrobials ceftolozane-tazobactam, ceftazidime-avibactam, and meropenem/vaborbactam are poorly active against resistant A. baumannii. The need to identify new antimicrobials active against A. baumannii is pressing. Background. We have demonstrated that the A. baumannii low molecular mass (LMM) penicillin binding protein 7/8 (PBP 7/8) is essential in vivo (i.e., required for bacterial survival in a host) in rat pneumonia and subcutaneous abscess infection models, and is required for survival in human serum and ascites. Our initial studies on PBP 7/8 were performed in an antimicrobial sensitive strain AB307-0294. These findings have since been confirmed with the extensively drug resistant (XDR) strain HUMC1. Since our initial observation other investigators, using INseq and Tn-seq, have shown that PBP 7/8 is needed for A. baumannii survival in the Galleria mellonella insect infection model and serum respectively. PBP 7/8 has many characteristics that support its potential as a high value drug target. However, based on studies in rich laboratory medium, LMM PBPs including PBP 7/8 have been perceived to be non-essential. As a result, PBP 7/8 have received scant attention as an antibacterial target and has not been considered for A. baumannii. However, our data contradicts this paradigm and endorses the need for additional studies on PBP 7/8 in XDR A. baumannii. Therefore, our objective is to validate PBP 7/8 as a drug target, delineate mechanisms that mediate its ex vivo and in vivo essentiality, and to identify compounds that inactivate PBP 7/8. Objectives and Methods. To achieve these objectives, studies on PBP 7/8 will be extended to include additional XDR strains of A. baumannii to confirm our findings are generalizable (aim 1). Aim 1 also will also explore mechanisms by which PBP 7/8 enables growth/survival of A. baumannii ex vivo and in vivo and identify the innate host defense factors it protects against. Increasing data support the need to treat infections due to XDR isolates with multiple agents, thereby increasing efficacy and protecting against the development of resistance. Our demonstration that the loss of PBP 7/8 production increases susceptibility to complement and lysozyme mediated bactericidal activity and changes cell structure supports the hypothesis that the inability to produce PBP 7/8 affects permeability, a critical factor in the intrinsic antimicrobial resistance of A. baumannii. Therefore, an additional goal of this proposal will be to assess the whether the loss of PBP 7/8 production enhances the activity of adjunctive therapy with antimicrobials and/or monoclonal antibodies directed against the capsule (aim 2). Additional studies in aim 2 will assess whether the loss of PBP 7/8 affects the production of other PBPs and ampC expression. These data will generate additional mechanistic insights into the consequences of not being able to produce PBP 7/8. Lastly, aim 3 will begin the process of identifying a “tool” compound that is active against PBP 7/8. A live wild-type XDR strain will be screened against a chemical library to identify compounds directed against PBP 7/8 that possess bactericidal activity. Additional orthogonal assays will establish specificity, determine their quality, and prioritize identified inhibitors for downstream optimization and pre-clinical studies. Deliverables from this proposal will validate the paradigm shift on the value of PBP 7/8 as an antimicrobial target and open an untapped venue for the development of a new class of antimicrobial agents against this XDR pathogen.