Deciphering the genetic basis of differential antibiotic efficacy in Enterococcus faecalis endocarditis

总结 粪肠球菌可引起感染性心内膜炎（IE），与E。faecalis IE 高达30%。治疗E.在过去十年中，粪肠球菌IE已从氨苄青霉素和庆大霉素 (AG)氨苄西林和头孢曲松（AC），由于先前的研究显示相同的疗效和改善的耐受性， AC.尽管AC在临床实践中迅速采用，但我们回顾了近200例E。faecalis IE在我们的 在过去的十年中，研究中心的研究显示，接受AC治疗的患者死亡率非常高。我们 研究了大肠杆菌的基因组流行病学。自2018年以来，我们中心的faecalis IE发现， 收集的菌株属于多位点序列类型ST 6和ST 179。所有ST 6分离株均携带突变 先前与低亲和力青霉素结合蛋白4（PBP 4）的过表达相关， 对β-内酰胺类、头孢菌素类和碳青霉烯类耐药。我们还发现所有ST 179分离株都具有 PBP 4（P520 S）编码序列中的突变，先前与β-内酰胺降低相关 亲和力我们使用棋盘试验测试了分离株对AC协同作用的敏感性，并观察到 ST 6分离株以及编码PP 2C型蛋白突变的分离株的协同作用降低 磷酸酶IreP最后，我们测试了AC如何有效地杀死E。使用单室 AC耐受的药代动力学-药效学（PK-PD）模型，发现ST 6和ST 179分离株 能够在AC暴露24-48小时后再生，而具有野生型PBP 4序列的不相关分离株 没有显示再生。在这里，我们提出测试的假设，E。导致IE的粪杆菌编码遗传特征 这会导致AC协同作用减弱，并可能导致某些患者的治疗失败。我们建议首先 研究大肠杆菌的基因组流行病学。faecalis IE在美国，并确定E.粪突变 与体外AC协同作用减弱有关。然后，我们将评估AC的药效学 针对遗传多样性E.粪肠球菌IE分离株，并将测试替代抗生素组合对分离株 对AC协同作用的敏感性降低。从AG到AC的实践变更是在不知情的情况下进行的 遗传多样性E.粪便对AC有反应，我们的初步数据表明，这种变化可能不会 使所有患者受益。有一个迫切需要确定是否E。粪肠易激综合征治疗范例 需要修订，如果需要，哪些替代组合可能最有效。我们的早期发现 表明并非所有E.粪肠杆菌IE分离株对AC的反应同样良好， 可能需要结合细菌基因型和定制的抗生素组合。通过强制 初步数据，拟议的研究将整合流行病学，基因组学和PK-PD方法，以解决 这些重要的问题。研究结果将为进一步验证最佳处理方案奠定基础 肠球菌IE的治疗策略，并将这些治疗方法转化为临床。

SUMMARY Enterococcus faecalis causes infective endocarditis (IE), and mortality rates associated with E. faecalis IE are as high as 30%. Treatment for E. faecalis IE has shifted over the last decade from ampicillin and gentamicin (AG) to ampicillin and ceftriaxone (AC), due to prior studies showing equal efficacy and improved tolerance of AC. Despite the rapid adoption of AC in clinical practice, our review of nearly 200 cases of E. faecalis IE at our center over the last decade showed strikingly high mortality rates among patients treated with AC. We investigated the genomic epidemiology of E. faecalis IE at our center since 2018, and found that 36% of all collected isolates belonged to multi-locus sequence types ST6 and ST179. All ST6 isolates harbored a mutation previously associated with overexpression of the low-affinity penicillin-binding protein 4 (PBP4) and increased resistance to beta-lactams, cephalosporins, and carbapenems. We also found that all ST179 isolates possessed a mutation in the coding sequence of PBP4 (P520S), that was previously correlated with lowered beta-lactam affinity. We tested isolates for their susceptibility to AC synergy using checkerboard assays, and observed decreased synergy for ST6 isolates, as well as for an isolate encoding a mutation in the PP2C-type protein phosphatase IreP. Finally, we tested how effectively AC could kill E. faecalis using a one-compartment pharmacokinetic-pharmacodynamic (PK-PD) model of AC tolerance, and found that ST6 and ST179 isolates were able to regrow after 24-48 hours of AC exposure, while an unrelated isolate with a wild type PBP4 sequence showed no regrowth. Here we propose to test the hypothesis that E. faecalis causing IE encode genetic features that cause diminished AC synergy and that may lead to treatment failure in some patients. We propose to first investigate the genomic epidemiology of E. faecalis IE in the United States, and to identify E. faecalis mutations that are associated with diminished AC synergy in vitro. Then, we will evaluate the pharmacodynamics of AC against genetically diverse E. faecalis IE isolates, and will test alternative antibiotic combinations against isolates with reduced susceptibility to AC synergy. The practice change from AG to AC has been made without knowing how genetically diverse E. faecalis respond to AC, and our preliminary data suggest that this change may not be benefiting all patients. There is an urgent need to determine whether the E. faecalis IE treatment paradigm requires revision, and if so, which alternative combinations are likely to be most effective. Our early findings indicate that not all E. faecalis IE isolates respond equally well to AC, and a more individualized approach that incorporates bacterial genotypes and tailored antibiotic combinations may be required. Enabled by compelling preliminary data, the proposed study will integrate epidemiologic, genomic, and PK-PD approaches to address these important questions. The results will lay the foundation for future studies to validate optimal treatment strategies for enterococcal IE, and to translate these treatments into the clinic.