Bacteriology Unit, Azienda Ospedaliero-Universitaria Pisana, via Paradisa 2, 56124, Pisa, Italy.
Department of Internal Medicine, Infectious Diseases Unit, University Hospital of Heraklion, Voutes, 71110, Heraklion, Crete, Greece; School of Medicine, European University Cyprus, 6 Diogenis Street, Engomi, Nicosia 1516, Cyprus.
Int J Antimicrob Agents. 2018 Feb;51(2):260-265. doi: 10.1016/j.ijantimicag.2017.10.011. Epub 2017 Oct 27.
mcr-1 has been reported as the first plasmid-encoded gene conferring colistin resistance. In KPC-producing Klebsiella pneumoniae (KPC-KP), however, colistin resistance is rapidly emerging through other mechanisms. Resistance is frequently due to disruption of the mgrB gene by insertion sequences, e.g. ISL3. The aim of this study was to investigate the expansion of mgrB-mutated KPC-KP isolates. In addition, the localisation and targets of ISL3 sequences within the core and accessory genome of common KPC-KP lineages were identified. A total of 29 clinical K. pneumoniae isolates collected from Italian patients were randomly selected. Whole genome sequences were analysed for resistance genes, plasmids and insertion sequences. In addition, 27 colistin-resistant KPC-KP isolates from a previous study from Crete (Greece) were assessed. Clonal expansion of KPC-KP isolates with various mutations in mgrB among all lineages was observed. In two Italian MLST ST512 isolates and eight Greek ST258 isolates, an identical copy of ISL3 was inserted in mgrB nucleotide position 133. ISL3, a transposable restriction-modification system of 8154 nucleotides, was located on pKpQIL-like plasmids and may transpose into the chromosome. In four isolates, chromosomal integration of ISL3 in diverse inner membrane proteins other than mgrB was identified. Colistin resistance is most often explained by clonal expansion of isolates with mutated mgrB. pKpQIL-like plasmids, which are omnipresent in KPC-KP, carry insertion sequences such as ISL3 that have mgrB as a target hotspot for transposition. Transposition of insertion sequences from plasmids and subsequent clonal expansion may contribute to the emerging colistin resistance in KPC-KP.
mcr-1 已被报道为第一个赋予粘菌素耐药性的质粒编码基因。然而，在产生 KPC 的肺炎克雷伯菌（KPC-KP）中，通过其他机制迅速出现粘菌素耐药性。耐药性通常是由于插入序列（例如 ISL3）破坏 mgrB 基因引起的。本研究旨在研究 mgrB 突变的 KPC-KP 分离株的扩展。此外，还确定了常见 KPC-KP 谱系核心和辅助基因组中 ISL3 序列的定位和靶标。从意大利患者中随机选择了 29 株临床分离的肺炎克雷伯菌。对全基因组序列进行了耐药基因、质粒和插入序列分析。此外，还评估了来自克里特岛（希腊）的先前研究中的 27 株粘菌素耐药的 KPC-KP 分离株。在所有谱系中，观察到 mgrB 中各种突变的 KPC-KP 分离株的克隆扩展。在两个意大利 MLST ST512 分离株和八个希腊 ST258 分离株中，ISL3 插入 mgrB 核苷酸位置 133 处的相同拷贝。ISL3 是一个 8154 个核苷酸的可移动限制修饰系统，位于 pKpQIL 样质粒上，可能转座到染色体上。在四个分离株中，除 mgrB 外，ISL3 还整合到不同的内膜蛋白中。粘菌素耐药性最常归因于 mgrB 突变的分离株的克隆扩展。pKpQIL 样质粒在 KPC-KP 中普遍存在，携带插入序列，如 ISL3，它是转座的 mgrB 靶热点。质粒和随后的克隆扩展的插入序列转座可能有助于 KPC-KP 中新兴的粘菌素耐药性。
