Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu Province, P. R. China.
Institute of Comparative Medicine, Yangzhou University, Yangzhou, Jiangsu Province, P. R. China.
J Antimicrob Chemother. 2019 Jun 1;74(6):1517-1520. doi: 10.1093/jac/dkz058.
To characterize the genome of an Escherichia coli harbouring both mcr-1 and mcr-3.19 on a hybrid plasmid and the underlying transmission mechanisms.
Broth microdilution was used to perform antimicrobial susceptibility testing. Conjugation assays and S1-PFGE were used to assess the transferability of mcr genes. Resistance genotypes and genetic contexts were investigated, based on WGS data from the Illumina and MinION platforms. Inverse PCR was performed to test the mcr-3.19-bearing circular intermediate. Bioinformatic tools were used to further characterize the hybrid plasmid.
E. coli CP53 was identified as harbouring both mcr-1 and mcr-3.19 on a 231 859 bp hybrid plasmid pCP53-mcr1_3 containing IncFIA, IncHI1A, IncHI1B and IncN replicons. The genetic structures of mcr-1 and mcr-3.19 were similar to those reported in other mcr-1 and mcr-3.19-bearing plasmids, which suggested that recombination between mcr-bearing plasmids had been mediated by ISs. However, the MDR plasmid pCP53-mcr1_3 cannot transfer via conjugation. Furthermore, another three plasmids were identified in the isolate, two of which encoded resistance genes. In640 duplication between two MDR plasmids was observed. An MDR-region recombination existed in E. coli CP53. A core structure consisting of mcr-3-dgkA existed in mcr-3-bearing plasmids reported, to date. Circular intermediates were observed for mcr-1 and mcr-3.19 regions.
A novel mcr-3.19 was identified along with mcr-1 contained in a hybrid plasmid. This finding suggested that evolution of mcr genes among various plasmids was being driven by mobile elements. Molecular surveillance of mcr gene co-occurrence warrants further investigation to evaluate the public health risk.
对同时携带 mcr-1 和 mcr-3.19 的大肠杆菌中混合质粒的基因组进行特征描述，并研究其潜在的传播机制。
采用肉汤微量稀释法进行抗菌药物敏感性试验。通过接合试验和 S1-PFGE 评估 mcr 基因的可转移性。根据 Illumina 和 MinION 平台的 WGS 数据，研究耐药基因型和遗传背景。通过反向 PCR 检测携带 mcr-3.19 的环状中间体。使用生物信息学工具进一步对混合质粒进行特征描述。
鉴定出大肠杆菌 CP53 同时携带 mcr-1 和 mcr-3.19，位于一个 231859bp 的混合质粒 pCP53-mcr1_3 上，该质粒包含 IncFIA、IncHI1A、IncHI1B 和 IncN 复制子。mcr-1 和 mcr-3.19 的遗传结构与其他 mcr-1 和 mcr-3.19 携带质粒报告的结构相似，这表明 mcr 携带质粒之间的重组是由 ISs 介导的。然而，MDR 质粒 pCP53-mcr1_3 不能通过接合进行转移。此外，在该分离株中还鉴定出另外三个质粒，其中两个编码耐药基因。在两个 MDR 质粒之间观察到 In640 重复。在大肠杆菌 CP53 中存在 MDR 区重组。迄今为止，在所报告的携带 mcr-3 的质粒中，存在一个由 mcr-3-dgkA 组成的核心结构。观察到 mcr-1 和 mcr-3.19 区域的环状中间体。
在混合质粒中发现了一种新型 mcr-3.19 与 mcr-1 同时存在。这一发现表明，各种质粒中 mcr 基因的进化是由移动元件驱动的。需要进一步进行 mcr 基因共存的分子监测，以评估公共卫生风险。
