Impact of Daptomycin Dose Exposure on Enterococci and Characterization of Resista

描述（由申请人提供）：万古霉素耐药肠球菌（VRE）引起的感染与治疗选择有限和死亡率增加有关。达托霉素是一种新型的脂肽类抗生素，具有抗VRE的活性。然而，目前尚不清楚用于VRE的达托霉素剂量如何优化患者预后并防止耐药性的出现。长期目标是通过使用理想剂量暴露和确定肠球菌中与达托霉素耐药相关的表型和基因型变化，优化结果并保持达托霉素治疗VRE感染。本研究的总体目标是确定达托霉素的剂量暴露断点（药代动力学/药理学[PK/PD]断点）和相关剂量，并确定是否在肠球菌中也发现了与金黄色葡萄球菌耐药相关的已知表型和基因型变化。中心假设是，较高的达托霉素剂量将提供更大的杀菌活性，并防止耐药性的出现。此外，耐达托霉素肠球菌的表型和遗传变化可能与金黄色葡萄球菌不同。提出这项研究的基本原理是，关于达托霉素剂量与肠球菌的关系的数据和对耐药机制的见解将导致临床剂量优化，改善患者预后，减少耐药的出现，并保留达托霉素作为临床使用的可行抗生素。中心假设将通过追求两个特定目标来验证：1)使用分子定义的VRE菌株和临床菌株确定达托霉素耐药的剂量暴露断点，以确定最佳剂量；2)通过体外PK/PD模型鉴定达托霉素耐药肠球菌细胞质膜和细胞壁相关的表型和遗传变化。在第一个目标下，将使用一个建立良好的体外模拟心内膜植被模型（先前针对动物心内膜炎模型进行验证）来确定利用各种临床剂量的达托霉素的断点（和相应的剂量）。在该模型中培养的达托霉素耐药菌株暴露于达托霉素后，将检查细胞壁、细胞质膜、基因序列和基因表达的变化。拟议的研究具有创新性，因为我们将利用体外PK/PD模型，该模型既模拟临床条件下的药物压力，又允许频繁评估生物体的变化，以获得要研究的达托霉素耐药突变体。本申请中提出的研究具有重要意义，因为它有望提供了解肠球菌耐药特性及其与达托霉素剂量暴露的关系所需的知识，从而导致剂量优化和改善患者预后。一旦掌握了这些知识，就会改善患者的预后，并保留达托霉素作为治疗肠球菌感染的可行治疗选择。

DESCRIPTION (provided by applicant): Infections caused by vancomycin resistant Enterococcus (VRE) are associated with limited treatment options and increased mortality. Daptomycin, a novel lipopeptide antibiotic, has activity against VRE. The daptomycin dose for VRE to optimize patient outcomes and prevent the emergence of resistance, however, is currently unknown. The long-term goal is to optimize outcomes and preserve daptomycin therapy for VRE infections through utilization of the ideal dose exposure and determination of phenotypic and genotypic changes associated with daptomycin resistance in enterococci. The overall objective of this study is to define the dose exposure breakpoint (pharmacokinetic/pharmacodynamic [PK/PD] breakpoint) for daptomycin and the correlating dose and determine if known phenotypic and genotypic changes associated with daptomycin resistance in S. aureus are also found in enterococci. The central hypothesis is that higher daptomycin doses will provide greater bactericidal activity and prevent the emergence of resistance. Additionally, phenotypic and genetic changes found in daptomycin resistant enterococci maybe different than those found in S. aureus. The rationale behind the proposed research is that data on the daptomycin dose relationship with enterococci and insights into the mechanisms of resistance will lead to clinical dose optimization, improved patient outcomes, reduced emergence of resistance, and preservation of daptomycin as a viable antibiotic for clinical use. The central hypothesis will be tested by pursuing two Specific Aims: 1) Determine the dose exposure breakpoints for daptomycin resistance using molecularly defined and clinical strains of VRE to determine the optimal dose; and 2) Identify phenotypic and genetic changes associated with the cytoplasmic membrane and the cell wall of daptomycin resistant enterococci derived from in vitro PK/PD models. Under the first aim, a well established in vitro model of simulated endocardial vegetations (previously validated against an animal endocarditis model) will be used to determine the breakpoints (and corresponding doses) utilizing various clinical doses of daptomycin. The daptomycin resistant strains developed in this model with daptomycin exposure will then be examined for changes in the cell wall, cytoplasmic membrane, gene sequences and gene expression. The proposed research is innovative because we will utilize an in vitro PK/PD model, which both simulates drug pressure under clinical conditions and allows for frequent assessment of changes in the organism, to derive the daptomycin resistant mutants to be studied. The research proposed in this application is significant because it is expected to provide the knowledge needed to understand the resistance characteristics of enterococci and their relationship to daptomycin dose exposure that will lead to dose optimization and improved patient outcomes. Once such knowledge is available, improved patient outcomes and the preservation of daptomycin as a viable therapeutic option for the treatment of enterococcal infections will result. PUBLIC HEALTH RELEVANCE: Narrative Preservation of available antibiotics to treat multidrug resistant bacterial infections is vital to public health. Vancomycin resistant enterococcal infections are associated with increased mortality and treatment options are limited. The overall goal of this project is to determine the optimal dose of daptomycin for enterococcal infections and increase current knowledge of the mechanisms of resistance, which will allow better understanding and treatment of this infectious disease.