Characterization of mcr-1-bearing Tn6330 in an E.coli strain by Nanopore Long Reads Accepted by Journal of Antimicrobial chemotherapy
Background Since the discovery of the plasmid-borne colistin resistance gene mcr-1 in late 2015,a flurry of studies has shown that the gene had already been circulating among members of Enterobacteriaceae in various countries for over a decade.Although this gene has been detectable mainly in plasmids and always found to be associated with the newly discovered ISApl1 element,direct evidence regarding the destiny of mcr-1,especially in Tn6330,is not available.Objectives To characterize the Tn6330 elements in both plasmid and chromosome in a single bacteria population with single-molecule long-read data.Methods Plasmid-borne and chromosomal Tn6330(ISApl1-mcr-1-orf-ISApl1)recovered from a colistin resistant Escherichia coli strain isolated from human feces were subjected to genetic characterization by PCR,conjugation,S1-PFGE,stability assay and whole genome sequencing.Various bioinformatic tools were utilized to analyze the heterogeneous structures of Tn6330.Results Tn6330 was also found in a plasmid and inserted in the E.coli chromosome simultaneously.The plasmid was found to comprise the IncFIB and a phage-like replicon,as well as two integrons that harbored various mobile elements and resistance genes including mcr-1,floR,blaTEM-1b,strAB.Interestingly,insertion elements were found to be distributed throughout the plasmid.Both plasmid-borne and chromosomal Tn6330 transposons could be re-organized into a circular intermediate that played a role in transmission of the mcr-1 gene.The decayed structure of Tn6330 in the genuine single DNA molecules of bacterial populations was detected for the first time,in which Tn6330 was degraded into a single ISApl1 element.Conclusions The Tn6330 was found to be very stable after 30 generation with or without colistin selective pressures through Nanopore long reads sequence analysis.These findings question the role of antibiotic exposure in resistance evolution and pave the way to further investigate transposon evolutionary dynamics by long-read technologies.
mcr-1 E.coli Tn6330 long reads
Ruichao Li Kaichao Chen Edward Wai-Chi Chan Sheng Chen
Shenzhen Key Lab for Food Biological Safety Control,Food Safety and Technology Research Center,Hong Shenzhen Key Lab for Food Biological Safety Control,Food Safety and Technology Research Center,Hong
国内会议
江苏扬州
英文
21-34
2019-04-01（万方平台首次上网日期，不代表论文的发表时间）