Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center, McGovern School of Medicine, Houston, TX, USA.
Division of Infectious Diseases, University of Texas Health Science Center, McGovern School of Medicine, Houston, TX, USA.
Mol Microbiol. 2019 Mar;111(3):811-824. doi: 10.1111/mmi.14193. Epub 2019 Jan 24.
The lipopeptide antibiotic daptomycin (DAP) is a key drug against serious enterococcal infections, but the emergence of resistance in the clinical setting is a major concern. The LiaFSR system plays a prominent role in the development of DAP resistance (DAP-R) in enterococci, and blocking this stress response system has been proposed as a novel therapeutic strategy. In this work, we identify LiaR-independent pathways in Enterococcus faecalis that regulate cell membrane adaptation in response to antibiotics. We adapted E. faecalis OG1RF (a laboratory strain) and S613TM (a clinical strain) lacking liaR to increasing concentrations of DAP, leading to the development of DAP-R and elevated MICs to bacitracin and ceftriaxone. Whole genome sequencing identified changes in the YxdJK two-component regulatory system and a putative fatty acid kinase (dak) in both DAP-R strains. Deletion of the gene encoding the YxdJ response regulator in both the DAP-R mutant and wild-type OG1RF decreased MICs to DAP, even when a functional LiaFSR system was present. Mutations in dak were associated with slower growth, decreased membrane fluidity and alterations of cell morphology. These findings suggest that overlapping stress response pathways can provide protection against antimicrobial peptides in E. faecalis at a significant cost in bacterial fitness.
脂肽类抗生素达托霉素(DAP)是治疗严重肠球菌感染的关键药物,但在临床环境中出现耐药性是一个主要问题。LiaFSR 系统在肠球菌中 DAP 耐药(DAP-R)的发展中起着重要作用,阻断这种应激反应系统已被提议作为一种新的治疗策略。在这项工作中,我们确定了粪肠球菌中与 LiaR 无关的途径,这些途径调节细胞膜适应抗生素的能力。我们使缺乏 liaR 的粪肠球菌 OG1RF(实验室菌株)和 S613TM(临床菌株)适应 DAP 的浓度增加,导致 DAP-R 的发展和 bacitracin 和头孢曲松 MIC 值升高。全基因组测序确定了 YxdJK 双组分调节系统和两种 DAP-R 菌株中一种假定的脂肪酸激酶(dak)的变化。在 DAP-R 突变体和野生型 OG1RF 中删除编码 YxdJ 反应调节剂的基因,即使存在功能性 LiaFSR 系统,也能降低 DAP 的 MIC 值。dak 突变与生长缓慢、膜流动性降低和细胞形态改变有关。这些发现表明,重叠的应激反应途径可以在显著降低细菌适应性的情况下,为粪肠球菌提供对抗抗菌肽的保护。