Molecular epidemiology of carbapenemase-producing Escherichia coli and the prevalence of ST131 subclone H30 in Shanghai, China

The molecular characteristics and epidemiology of carbapenemase-producing Escherichia coli (CPEC) isolates from Shanghai, China, were investigated using 21 imipenem-resistant E. coli isolates obtained from a Shanghai teaching hospital from 2011 to 2014. The presence of blaKPC, blaIMP, blaVIM, blaOXA-48, and blaNDM was assessed by polymerase chain reaction (PCR) amplification and sequencing. CPEC isolates were characterized by the Etest®, multilocus sequence typing (MLST), and pulse-field gel electrophoresis (PFGE). Plasmids carrying resistance genes were analyzed by conjugation experiments, replicon typing, plasmid MLST (pMLST), S1 nuclease PFGE (S1-PFGE), and Southern hybridization. The genetic environment of the resistance genes was determined by PCR and sequencing. Among the 21 E. coli isolates, 16 produced carbapenemases; of these, ten isolates transferred carbapenemase-encoding plasmids to recipient bacteria. Nine of the 16 isolates were clonally related, and their PFGE patterns were designated type A. ST131 was the predominant sequence type (11 isolates, 68.8 %); the H30 subclone comprised 81.8 % of the ST131 strains. In all three isolates, blaIMP-4 was located on 50-kb IncN plasmids. All but two blaKPC-2 genes were carried on IncF plasmids of various sizes. Hence, both clone-spread and horizontal transfer mediated the dissemination of carbapenemase-producing genes in the Shanghai isolates.