<p>Co-Occurrence of the <em>mcr-1.1</em> and <em>mcr-3.7</em> Genes in a Multidrug-Resistant <em>Escherichia coli</em> Isolate from China</p>
Chongtao Du, Yuyang Feng, Guizhen Wang, Zhiyuan Zhang, Huimin Hu, Yu Yu, Jiayang Liu, Lihao Qiu, Hongtao Liu, Zhimin Guo, Jing Huang, Jiazhang Qiu
Abstract
Objective: A colistin-resistant Escherichia coli strain isolated from dog feces was characterized in this study. Methods and Results: A multiplex PCR assay was used to detect the presence of colistin-resistant mcr genes; it was found that E. coli QDFD216 co-harbored the mcr-1 and mcr-3 genes. Whole-genome sequencing and further bioinformatics analysis revealed that E. coli QDFD216 belonged to serotype O176:H11, fimH1311 type and ST132. The resistance genes bla CTX-M-14 , mdfA, dfrA3, acrA, acrB, tolc , and sul3 were present in the chromosome. The mcr-1.1 and mcr-3.7 genes were located in two plasmids of different incompatibility groups. mcr-1.1 was carried by a IncX4-type plasmid within an typical IS 26-parA-mcr-1.1-pap2 cassette, while mcr-3.7 was encoded by an IncP1-type plasmid with a genetic structure of Tn As2-mcr-3.7-dgkA -IS 26 . No additional antibiotic resistance genes were carried by either plasmid. Conclusion: This is the first report of an E. coli isolate co-harboring a mcr-1.1 -carrying IncX4 plasmid and a mcr-3.7 -carrying IncP1 plasmid. The evolution and mechanism of mcr gene co-existence need further study to assess its impact on public health. Keywords: colistin resistance, whole-genome sequencing, mcr genes, mcr-1 , mcr-3