Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, China.
Division of Infectious Diseases, State Key Laboratory of Biotherapy, Chengdu, China.
J Antimicrob Chemother. 2018 Sep 1;73(9):2336-2339. doi: 10.1093/jac/dky226.
New Delhi MBL (NDM) is a type of carbapenemase; 20 variants of NDM have been identified to date. We have found a new variant of NDM, NDM-21, and describe it here.
A carbapenem-resistant Escherichia coli was subjected to WGS using an Illumina X10 sequencer to identify the antimicrobial resistance genes and its ST. The gene encoding the new variant of NDM was cloned into E. coli DH5α, with blaNDM-5 being cloned as the control. Transformants were tested for susceptibility to carbapenems. Mating was performed to obtain the plasmid carrying the new blaNDM gene and the complete plasmid sequence was obtained using long-read MinION sequencing.
The E. coli isolate belonged to ST617 and phylogenetic group A. It had a gene encoding NDM-21, a new NDM variant. NDM-21 differs from NDM-5 by a Gly-to-Ser amino acid substitution at position 69 (G69S). NDM-21 retains the same activity against carbapenems as NDM-5. blaNDM-21 is carried by a 46.1 kb IncX3 plasmid, which is self-transmissible, and is located in a complex genetic context as blaNDM-5. The isolate also carried blaCTX-M-55, which encodes an ESBL conferring resistance to aztreonam (which completed its resistance to all clinically available β-lactams), and rmtB, which mediates high-level resistance to aminoglycosides, on an IncFII plasmid.
A new NDM variant has been identified and blaNDM-21 has evolved from blaNDM-5 on an IncX3 plasmid.
新德里金属-β-内酰胺酶（NDM）是一种碳青霉烯酶；迄今为止，已鉴定出 20 种 NDM 变体。我们发现了一种新的 NDM 变体，即 NDM-21，并对其进行了描述。
对一株耐碳青霉烯的大肠埃希菌进行 WGS 分析，使用 Illumina X10 测序仪鉴定其抗生素耐药基因及其 ST。将编码新 NDM 变体的基因克隆到大肠埃希菌 DH5α中，以 blaNDM-5 作为对照。对转化子进行碳青霉烯类药物敏感性测试。通过交配获得携带新 blaNDM 基因的质粒，并使用长读长 MinION 测序获得完整质粒序列。
该大肠埃希菌分离株属于 ST617 和 A 群。它具有编码 NDM-21 的基因，这是一种新的 NDM 变体。NDM-21 与 NDM-5 的区别在于第 69 位的甘氨酸到丝氨酸的氨基酸取代（G69S）。NDM-21 对碳青霉烯类药物的活性与 NDM-5 相同。blaNDM-21 由一个 46.1kb 的 IncX3 质粒携带，该质粒可自我传递，并且位于 blaNDM-5 所在的复杂遗传环境中。该分离株还携带 blaCTX-M-55，它编码一种对氨曲南（使其对所有临床可用的β-内酰胺类药物均耐药）耐药的 ESBL，以及 rmtB，它介导对氨基糖苷类药物的高水平耐药，位于 IncFII 质粒上。
已鉴定出一种新的 NDM 变体，blaNDM-21 是由 IncX3 质粒上的 blaNDM-5 进化而来的。
