| Summary: | Ying Li,1,2,* Min Tang,3,* Xiaoyi Dai,4,5 Yingshun Zhou,4,5 Zhikun Zhang,4,5 Yichuan Qiu,4,5 Chengwen Li,1,2 Luhua Zhang4,5 1Department of Immunology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan, People’s Republic of China; 2Immunological Technology Platform, Southwest Medical University, Luzhou, Sichuan, People’s Republic of China; 3Department of Laboratory Medicine, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, People’s Republic of China; 4Department of Pathogenic Biology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, Sichuan, People’s Republic of China; 5Pathogen Biology Platform, Southwest Medical University, Luzhou, Sichuan, People’s Republic of China*These authors contributed equally to this workCorrespondence: Luhua Zhang; Chengwen Li Xiang Lin Road, Longmatan District, Luzhou City, Sichuan Province, 646000, People’s Republic of ChinaTel/Fax +86-0830-3160073Email zhluhua@swmu.edu.cn; Lichw110119@163.comPurpose: Three NDM-5-producing Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, and Citrobacter braakii, one each) were isolated during a screening study for the presence of carbapenemase-producing Enterobacteriaceae (CPE) strains in urban rivers in China. The aim of the present study was to characterize these NDM-5-producing isolates by using whole-genome analysis.Methods: In vitro susceptibility testing was performed using the broth microdilution method. Conjugation assay was carried out to investigate the transferability of blaNDM-5-harboring plasmids. Whole-genome sequencing was performed using an Illumina HiSeq combined with the PacBio RSII system. The genetic characteristics of the blaNDM-5-harboring plasmids were analyzed. Antimicrobial resistance genes and virulence genes were identified from the genome sequences. Phylogenetic analysis was performed based on core genome.Results: Antimicrobial susceptibility testing showed that all three isolates were resistant to carbapenems, cephalosporins, quinolones, and aminoglycosides, and susceptible to colistin. Whole-genome sequencing showed that each isolate carried multiple antibiotic resistance genes mediating multidrug resistance, and harbored numerous virulence genes, some of which were located on plasmids. In these isolates, blaNDM-5 was carried by an IncX3 plasmid in K. pneumoniae and C. braakii, and on an IncR/IncX1 plasmid in E. coli. Conjugation experiments showed that these blaNDM-5-haboring plasmids were successfully transferred to E. coli J53. Phylogenetic analysis revealed that E. coli SCLZR49 was present in a cluster with isolates of different origin, K. pneumoniae SCLZR50 was mainly clustered with clinical isolates, and C. braakii SCLZR53 had closely genetic relationship with environmental isolates.Conclusion: This study revealed contamination of the urban river ecosystems by clinically significant carbapenemase gene blaNDM-5, raising the possibility of plasmid transmission into the environmental from humans and highlighting the need for a constant surveillance of CPE in the environment under the “One-Health” perspective.Keywords: carbapenemase, antimicrobial resistance, aquatic environment, river water
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