Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, China; Division of Infectious Diseases, State Key Laboratory of Biotherapy, Chengdu, China.
Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
J Glob Antimicrob Resist. 2019 Jun;17:90-93. doi: 10.1016/j.jgar.2018.11.017. Epub 2018 Nov 26.
Here we report the finding of three copies of the bla gene on a plasmid in ST11 Klebsiella pneumoniae.
Carbapenem-resistant K. pneumoniae clinical strain WCHKP2 was subjected to whole-genome sequencing (WGS) using both a short-read Illumina HiSeq X10 platform and long-read MinION sequencer. Hybrid assembly was performed using Unicycler, and contigs were corrected using Pilon. Based on WGS, the sequence type (ST), capsular type, plasmid replicon type and plasmid multilocus sequence type were determined and virulence and antimicrobial resistance genes were identified. Mating was performed to identify a self-transmissible plasmid mediating carbapenem resistance.
Strain WCHKP2 was resistant to imipenem [minimum inhibitory concentration (MIC)=64μg/mL] and meropenem (MIC=128μg/mL). Strain WCHKP2 had a 5477148-bp circular chromosome, two small ColRNAI-like plasmids (5596bp and 10060bp), and one large plasmid (177516bp, designated pKPC2_020002) containing an IncR and an IncFII replicon. Surprisingly, there were three copies of the bla carbapenemase gene on pKPC2_020002, which was not self-transmissible. Each of the bla genes was located in the same genetic context with insertion sequence ISKpn27 upstream and ISKpn6 downstream and bracketed by IS26. The three copies of the IS26-ISKpn27-bla-ISKpn6-IS26 unit were present in tandem.
Here we report the surprising co-existence of three copies of bla on an IncR/IncF plasmid due to the action of IS26. Multiple copies of IS26 are a key factor generating genetic plasticity and could mediate the multiplication of resistance genes.
本研究报告了 ST11 型肺炎克雷伯菌质粒上存在 bla 基因的三个拷贝。
对耐碳青霉烯肺炎克雷伯菌临床株 WCHKP2 进行全基因组测序（WGS），使用短读长 Illumina HiSeq X10 平台和长读长 MinION 测序仪。使用 Unicycler 进行杂交组装，使用 Pilon 校正重叠群。基于 WGS，确定序列型（ST）、荚膜型、质粒复制子类型和质粒多位点序列型，并鉴定毒力和抗菌药物耐药基因。进行交配实验以鉴定介导碳青霉烯类耐药的可自我传播质粒。
菌株 WCHKP2 对亚胺培南（MIC=64μg/mL）和美罗培南（MIC=128μg/mL）耐药。菌株 WCHKP2 有一个 5477148bp 的环状染色体，两个小的 ColRNAI 样质粒（5596bp 和 10060bp）和一个大质粒（177516bp，命名为 pKPC2_020002），包含 IncR 和 IncFII 复制子。令人惊讶的是，pKPC2_020002 上有 bla 碳青霉烯酶基因的三个拷贝，但其不能自我传播。每个 bla 基因都位于相同的遗传环境中，上游有插入序列 ISKpn27，下游有 ISKpn6，由 IS26 隔开。三个 IS26-ISKpn27-bla-ISKpn6-IS26 单元串联存在。
本研究报告了令人惊讶的是，由于 IS26 的作用，IncR/IncF 质粒上同时存在 bla 基因的三个拷贝。多个 IS26 拷贝是产生遗传可塑性的关键因素，并可介导耐药基因的增殖。
