VraSR Two-Component Regulatory System Contributes to mprF-Mediated Decreased Susceptibility to Daptomycin in In Vivo-Selected Clinical Strains of Methicillin-Resistant Staphylococcus aureus
VraSR Two-Component Regulatory System Contributes to mprF-Mediated Decreased Susceptibility to Daptomycin in In Vivo-Selected Clinical Strains of Methicillin-Resistant Staphylococcus aureus
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DOI：
10.1128/aac.00432-10
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发表时间：
2012-01-01
影响因子：
4.9
通讯作者：
Rosato, Adriana E.
中科院分区：
文献类型：
--
作者：
Mehta, Shrenik;Cuirolo, Arabela X.;Rosato, Adriana E.
达托霉素（DAP）是一种新型的环脂肽抗生素，对耐甲氧西林金黄色葡萄球菌（MRSA）感染具有高度活性。提出的机制涉及以Ca依赖性方式破坏细菌膜的功能完整性。在本工作中，我们研究了一组从S.金黄色葡萄球菌感染治疗后与DAP。在DAP耐药（DR）菌株中发现了mprF基因的不同点突变。DR菌株中mprF L826 F突变的研究是通过DAP敏感（DS）菌株中全长野生型或突变mprF的失活和反式互补来完成的，揭示了它们与DR表型的机械联系。然而，我们的数据表明，mprF不是决定对DAP耐药性的唯一因素。差异基因表达分析表明，上调的双组分调控系统vraSR。vraSR的失活导致DAP敏感性增加，而vraSR突变株的互补使DAP抗性恢复至与相应DR野生型菌株中观察到的水平相当的水平。电子显微镜分析显示DR CB 5012的细胞壁比DS CB 5011厚，这一效应与细胞壁中vraSR和mprF突变的影响相关。此外，DS菌株中vraSR的过表达导致对DAP的抗性增加和对苯唑西林的抗性降低，与DR菌株中观察到的表型相似。这些结果支持了以下建议：除了mprF突变外，vraSR还有助于本临床菌株组中的DAP耐药性。
Daptomycin (DAP) is a new class of cyclic lipopeptide antibiotic highly active against methicillin-resistant Staphylococcus aureus (MRSA) infections. Proposed mechanisms involve disruption of the functional integrity of the bacterial membrane in a Ca-dependent manner. In the present work, we investigated the molecular basis of DAP resistance in a group of isogenic MRSA clinical strains obtained from patients with S. aureus infections after treatment with DAP. Different point mutations were found in the mprF gene in DAP-resistant (DR) strains. Investigation of the mprF L826F mutation in DR strains was accomplished by inactivation and transcomplementation of either full-length wild-type or mutated mprF in DAP-susceptible (DS) strains, revealing that they were mechanistically linked to the DR phenotype. However, our data suggested that mprF was not the only factor determining the resistance to DAP. Differential gene expression analysis showed upregulation of the two-component regulatory system vraSR. Inactivation of vraSR resulted in increased DAP susceptibility, while complementation of vraSR mutant strains restored DAP resistance to levels comparable to those observed in the corresponding DR wild-type strain. Electron microscopy analysis showed a thicker cell wall in DR CB5012 than DS CB5011, an effect that was related to the impact of vraSR and mprF mutations in the cell wall. Moreover, overexpression of vraSR in DS strains resulted in both increased resistance to DAP and decreased resistance to oxacillin, similar to the phenotype observed in DR strains. These results support the suggestion that, in addition to mutations in mprF, vraSR contributes to DAP resistance in the present group of clinical strains.