Molecular Epidemiology Of Carbapenemase Producing Esherichia Coli And The Mechanism Of Drug Resistance

Objective Investigate the mechanism of carbapenem resistancein 121 carbapenem-non-susceptible clinical isolates of Esherichia coli(E.coli)by detection of carbapenemase and?-lactamase.Investigate the molecular epidemiology by molecular classification technologies.Methods The minimum inhibitory concentrations(MICs)of antimicrobials to E.coli isolates were determined by agar dilution method.The molecular mechanisms of carbapenem resistance of E.coli isolates were analyzed by PCRs,DNA sequencing and conjugation experiment.Pulsed-field gel electrophoresis(PFGE)and multilocus sequence typing(MLST)were performed to analyze the molecular epidemiology of carbapenemase producing E.coli.Results A total of 121 carbapenem-non-susceptible E.coli were isolated.The MICs to meropenem,imipenem and ertapenem ranged from 2 to 256?g/ml,4 to>256?g/ml,4 to>256?g/ml,respectively,and the resistance level to other(3-lactams and ciprofloxacin were high.97 isolates produced KPC-2 carbapenemase,4 isolates produced NDM-1 carbapenemase,and 20 isolates did not produce any carbapenemase.?-lactamase of TEM-1 and the group of CTX-M-1/-M-9 were highly detected,and majority produced more than one?-lactamase.Carbapenem resistance can be transferred to J53 from most isolates(103 isolates)by conjugation.Part of these isolates were indistinguishable or closely related to each other as indicated by PFGE.Fourteen sequence types were identified by MLST,in which ST131(51 isolates)and ST405(29 isolates)were most prevalent.Conclusions Carbapenem resistance in E.coli was mainly due to production of carbapenemases,especially KPC-2,clonal spread existed in our hospital.E.coli isolates producing NDM-1 were isolated in the year of 2013 and 2014,which showed clonal diversity.ST131 and ST405 were the predominant STs of carbapenemase producing E.coli.