IS5 Element Integration, a Novel Mechanism for Rapid In Vivo Emergence of Tigecycline Nonsusceptibility in Klebsiella pneumoniae
IS5 Element Integration, a Novel Mechanism for Rapid In Vivo Emergence of Tigecycline Nonsusceptibility in Klebsiella pneumoniae
复制标题
DOI：
10.1128/aac.03053-14
复制
发表时间：
2014-10-01
影响因子：
4.9
通讯作者：
Lesho, Emil P.
中科院分区：
文献类型：
--
作者：
Nielsen, Lindsey E.;Snesrud, Erik C.;Lesho, Emil P.
替加环素的不敏感性令人担忧，因为替加环素越来越多地用于治疗碳青霉烯类或粘菌素耐药微生物。在肠杆菌科中，替加环素不敏感性由AcrAB-TolC外排泵介导，泵活性通常是其转录调节因子、同源阻遏基因或非编码区突变的下游效应，如肠杆菌科和不动杆菌属分离株所示。在此，我们报告了在替加环素治疗期间收集的一系列多重耐药（MDR）和广泛耐药（XDR）肺炎克雷伯菌分离株中出现替加环素不敏感性，并阐明了其耐药机制。在替加环素治疗一名2.5个月大的新生儿之前和期间回收临床分离株。对替加环素的抗菌药物敏感性试验确定，在替加环素治疗完成之前，MIC从1 μ g/ml增加到4 μ g/ml。与其他研究不同的是，我们通过逆转录-定量PCR（qRT-PCR）未发现拉马、ramR、oqxA、acrB、marA或rarA基因的表达增加。全基因组测序显示IS 5插入元件在非敏感菌株上游85 bp的推定外排泵操纵子，这里命名为kpgABC，以前未知的参与耐药。在非kpgABC背景中引入kpgABC基因使替加环素的MIC增加4倍，并且不依赖于功能性AcrAB-TolC泵。这是第一份报告，提出了一个功能的kpgABC和确定的插入元件，其存在与在体内发展的替加环素不敏感的K。肺炎。
Tigecycline nonsusceptibility is concerning because tigecycline is increasingly relied upon to treat carbapenem-or colistin-resistant organisms. In Enterobacteriaceae, tigecycline nonsusceptibility is mediated by the AcrAB-TolC efflux pump, among others, and pump activity is often a downstream effect of mutations in their transcriptional regulators, cognate repressor genes, or non-coding regions, as demonstrated in Enterobacteriaceae and Acinetobacter isolates. Here, we report the emergence of tigecycline nonsusceptibility in a longitudinal series of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Klebsiella pneumoniae isolates collected during tigecycline therapy and the elucidation of its resistance mechanisms. Clinical isolates were recovered prior to and during tigecycline therapy of a 2.5-month-old Honduran neonate. Antimicrobial susceptibility tests to tigecycline determined that the MIC increased from 1 to 4 mu g/ml prior to the completion of tigecycline therapy. Unlike other studies, we did not find increased expression of ramA, ramR, oqxA, acrB, marA, or rarA genes by reverse transcription-quantitative PCR (qRT-PCR). Whole-genome sequencing revealed an IS5 insertion element in nonsusceptible isolates 85 bp upstream of a putative efflux pump operon, here named kpgABC, previously unknown to be involved in resistance. Introduction of the kpgABC genes in a non-kpgABC background increased the MIC of tigecycline 4-fold and is independent of a functional AcrAB-TolC pump. This is the first report to propose a function for kpgABC and identify an insertion element whose presence correlated with the in vivo development of tigecycline nonsusceptibility in K. pneumoniae.