Emergence of High-Level Colistin Resistance in an Acinetobacter baumannii Clinical Isolate Mediated by Inactivation of the Global Regulator H-NS
Emergence of High-Level Colistin Resistance in an Acinetobacter baumannii Clinical Isolate Mediated by Inactivation of the Global Regulator H-NS
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DOI：
10.1128/aac.02442-17
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发表时间：
2018-07-01
影响因子：
4.9
通讯作者：
Boyce, John D.
中科院分区：
文献类型：
--
作者：
Lucas, Deanna Deveson;Crane, Bethany;Boyce, John D.
粘菌素是一种关键的最后一线药物，用于治疗由革兰氏阴性细菌鲍曼不动杆菌的多重耐药菌株引起的危及生命的感染。然而，粘菌素耐药的A.在粘菌素治疗失败后仍然可以分离鲍曼不动杆菌分离株。耐药性最常由PmrC向脂质A添加磷酸乙醇胺（pEtN）介导，随后编码PmrC的pmrCAB操纵子和双组分信号转导系统PmrA/PmrB发生错义突变。我们找到了一对A在粘菌素治疗失败之前（6009-1）和之后（6009-2）从单个患者分离的鲍曼不动杆菌。这些菌株分别显示出低水平和非常高水平的粘菌素抗性（MIC，8至16 μ g/ml和128 μ g/ml）。为了了解粘菌素耐药性是如何增加的，我们对每个分离株的基因组进行了测序，结果显示6009-2在编码H-NS家族转录调节因子的基因内有一个额外拷贝的插入序列元件ISAba 125。为了证实H-NS在粘菌素抗性中的作用，我们在6009-1中产生了hns缺失突变体，并且显示在hns缺失后粘菌素抗性增加。我们还提供了6009-2的hns基因的完整拷贝，并表明该菌株对高浓度的粘菌素不再具有耐药性。临床分离株的转录组学分析鉴定了150多个基因在粘菌素耐药hns突变体6009-2中的差异表达。重要的是，在hns突变体中，编码第二个脂质A特异性pEtN转移酶但不编码pmrC的eptA的表达增加。这是第一次H-NS家族转录调节因子与pEtN转移酶和粘菌素抗性相关。
Colistin is a crucial last-line drug used for the treatment of life-threatening infections caused by multidrug-resistant strains of the Gram-negative bacterium Acinetobacter baumannii. However, colistin-resistant A. baumannii isolates can still be isolated following failed colistin therapy. Resistance is most often mediated by the addition of phosphoethanolamine (pEtN) to lipid A by PmrC, following missense mutations in the pmrCAB operon encoding PmrC and the two-component signal transduction system PmrA/PmrB. We recovered a pair of A. baumannii isolates from a single patient before (6009-1) and after (6009-2) failed colistin treatment. These strains displayed low and very high levels of colistin resistance (MICs, 8 to 16 mu g/ml and 128 mu g/ml), respectively. To understand how increased colistin resistance arose, we sequenced the genome of each isolate, which revealed that 6009-2 had an extra copy of the insertion sequence element ISAba125 within a gene encoding an H-NS family transcriptional regulator. To confirm the role of H-NS in colistin resistance, we generated an hns deletion mutant in 6009-1 and showed that colistin resistance increased upon the deletion of hns. We also provided 6009-2 with an intact copy of hns and showed that the strain was no longer resistant to high concentrations of colistin. Transcriptomic analysis of the clinical isolates identified more than 150 genes as being differentially expressed in the colistin-resistant hns mutant 6009-2. Importantly, the expression of eptA, encoding a second lipid A-specific pEtN transferase but not pmrC, was increased in the hns mutant. This is the first time an H-NS family transcriptional regulator has been associated with a pEtN transferase and colistin resistance.