State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China.
Department of Veterinary Medicine, Centre for Infection Medicine, Institute of Microbiology and Epizootics, Freie Universität Berlin, Berlin, Germany.
J Antimicrob Chemother. 2019 Jul 1;74(7):1799-1806. doi: 10.1093/jac/dkz107.
To characterize an MDR blaIMP-4-harbouring plasmid from Enterobacter cloacae EC62 of swine origin in China.
Plasmid pIMP-4-EC62 from E. cloacae EC62 was transferred by conjugation via filter mating into Escherichia coli J53. Plasmid DNA was extracted from an E. coli J53 transconjugant and sequenced using single-molecule real-time (SMRT) technology. MIC values for both the isolate EC62 and the transconjugant were determined using the broth microdilution and agar dilution methods. Plasmid stability in both the isolate EC62 and the transconjugant was assessed through a series of passages on antibiotic-free media.
Plasmid pIMP-4-EC62 is 314351 bp in length, encodes 369 predicted proteins and harbours a novel class 1 integron carrying blaIMP-4 and a group II intron. The blaIMP-4-bearing plasmid belongs to the IncHI2/ST1 incompatibility group. Sequence analysis showed that pIMP-4-EC62 carries four MDR regions and several gene clusters encoding heavy metal resistance. Plasmid pIMP-4-EC62 was stably maintained in both the E. cloacae EC62 isolate and the transconjugant E. coli J53-pIMP-4-EC62 in the absence of selective pressure. Analysis of the evolutionary relatedness of selected IncHI2 plasmids indicates that ST1-type plasmids are key carriers of carbapenemase genes among IncHI2 plasmids.
pIMP-4-EC62 represents the first fully sequenced IncHI2-type blaIMP-4-harbouring plasmid from E. cloacae in China. Co-location of blaIMP-4 with other resistance genes on an MDR plasmid is likely to further accelerate the dissemination of blaIMP-4 by co-selection among bacteria from humans, animals and the environment under the selective pressure of other antimicrobial agents, heavy metals and disinfectants.
对一株来源于中国猪源阴沟肠杆菌 EC62 的 MDR blaIMP-4 质粒进行特征分析。
通过滤膜接合将阴沟肠杆菌 EC62 中的质粒 pIMP-4-EC62 转移到大肠杆菌 J53 中。从大肠杆菌 J53 转导子中提取质粒 DNA，并使用单分子实时 (SMRT) 技术进行测序。采用肉汤微量稀释法和琼脂稀释法测定分离株 EC62 和转导子的 MIC 值。通过在无抗生素培养基上进行一系列传代实验来评估分离株 EC62 和转导子中质粒的稳定性。
质粒 pIMP-4-EC62 长 314351bp，编码 369 个预测蛋白，携带一个新型的 class 1 整合子，包含 blaIMP-4 和一个 group II 内含子。携带 blaIMP-4 的质粒属于 IncHI2/ST1 不相容群。序列分析表明，pIMP-4-EC62 携带四个 MDR 区和几个编码重金属抗性的基因簇。在没有选择压力的情况下，pIMP-4-EC62 可稳定地存在于阴沟肠杆菌 EC62 分离株和转导子大肠杆菌 J53-pIMP-4-EC62 中。对选定的 IncHI2 质粒进化关系的分析表明，ST1 型质粒是 IncHI2 质粒中 carbapenemase 基因的主要载体。
pIMP-4-EC62 代表了中国阴沟肠杆菌中首个完全测序的 IncHI2 型 blaIMP-4 质粒。在其他抗菌药物、重金属和消毒剂的选择压力下，blaIMP-4 与其他耐药基因位于一个 MDR 质粒上，这可能会通过细菌之间的共选择，加速 blaIMP-4 的传播。
