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Yi Yuan,1,* Ying Li,2,* Guangxi Wang,3 Chengwen Li,2 Li Xiang,3 Junping She,3 Yan Yang,3 Fangcai Zhong,1 Luhua Zhang3 1Department of Clinical Laboratory, The First People’s Hospital of Neijiang, Sichuan, People’s Republic of China; 2Department of Immunology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan, People’s Republic of China; 3Department of Pathogenic Biology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan, People’s Republic of China*These authors contributed equally to this workCorrespondence: Luhua ZhangDepartment of Pathogenic Biology, School of Basic Medical Sciences, Southwest Medical University, Xiang Lin Road, Longmatan District, Luzhou City 646000, Sichuan Province, People’s Republic of ChinaTel/Fax +86 830 3160073Email zhluhua@swmu.edu.cnBackground: Colistin acts as the last line of defense against severe infections caused by carbapenem-resistant Enterobacteriaceae. Infections caused by extensively drug-resistant isolates coproducing MCR and carbapenemases have posed a serious public health concern.Purpose: In this study, we reported the first clinical colistin and carbapenem-resistant Enterobacter hormaechei isolate SCNJ07 coharboring blaNDM-1 and mcr-9 from a patient with bloodstream infection in China.Methods: Bacterial antimicrobial susceptibility testing was performed using the broth microdilution method. Conjugation assay was carried out to investigate the transferability of mcr-9 and blaNDM-1. Whole-genome sequencing of strain SCNJ07 was performed using an Illumina HiSeq system and the genetic characteristics of the mcr-9- and blaNDM-1-harboring plasmids were analyzed.Results: Conjugation assays revealed that both blaNDM-1 and mcr-9 genes could successfully transfer their resistance phenotype to Escherichia coli strain J53. Whole genome sequencing showed that SCNJ07 possessed an FIB36:FIIY4 type self-transmissible plasmid bearing blaNDM-1, which possessed high similarity to previously reported pRJF866 in China. mcr-9 was located on a ∼28-kb self-transmissible plasmid pMCR-SCNJ07 with both IncHI2 and IncR replicons. Two copies of intact IS903 that bracketed a ∼8-kb region containing the mcr-9 gene were identified in pMCR-SCNJ07. BLASTn analysis revealed that a number of mcr-9-positive plasmids have been around for a while among Enterobacteriaceae worldwide.Conclusion: This study reveals the likelihood of a wide dissemination of this newly identified colistin resistance gene mcr-9 among Enterobacteriaceae. Further surveillance is urgently needed to understand the prevalence and dissemination of mcr-9, thereby facilitating establishment of measures to control its spread.Keywords: colistin, mcr-9, CRE, IS903 |
