多重耐药大肠杆菌QL57EC全基因组测序分析及转座子Tn7772鉴定OA

[Objective]The plasmids carried by the multi-drug resistant Escherichia coli strain QL57EC were analyzed,and the drug-resistance genes and mobile genetic elements were identified to provide a scientific basis for the IS26-mediated pseudocomplex transposon promoting horizontal transmission of drug-resistance genes of antibacterial agents.[Method]Taking the novel plasmid carried by the multi-drug resistant E.coli strain QL57EC,which was isolated from healthy pig feces,as the research subject,its antimicrobial resistance was determined by the antimicrobial susceptibility test,the plasmid was identified via genome-wide sequencing and bioinformatics analysis,and its mobility was verified through conjugation and transformation experiments.[Result]E.coli strain QL57EC carried two plasmids of pQL57EC-1(128 880 bp,containing 172 open reading frames,51.74%G+C content)and pQL57EC-2(113 349 bp,containing 130 open reading frames,46.91%G+C content).The plasmid pQL57EC-1 and pQL57EC-2 belonged to IncF-FIB/IncX1 and IncF-FIB incompatibility group,respectively.The plasmid pQL57EC-1 carried a novel transposon Tn7772,with IS26 insertion sequences at both ends,and the transposon was detected in both E.coli from healthy pig and Salmonella isolated from human faces.The conjugation test of E.coli strain QL57EC was unsuccessful,but the plasmid pQL57EC-1 could be transferred into E.coli strain DH5α by the transformation test.[Conclusion]E.coli strain QL57EC carries plasmid pQL57EC-1 and pQL57EC-2.Among them,the novel plasmid pQL57EC-1 carries a novel transposon Tn7772,which can serve as a repository for antibiotic resistance genes and for promoting cross-species transmission.It is speculated that it may pose a threat to human and animal health.