Emergence of KPC-2-producing Escherichia coli isolates in an urban river in Harbin, China

Three KPC-2-producing Escherichia coli (E1, E2, and E3) were recovered from water samples of an urban river in the city of Harbin, China. Antimicrobial susceptibility was determined by broth microdilution. Molecular characterization and genetic relatedness of the isolates were determined by polymerase chain reaction (PCR), pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and PCR-directed phylotyping. Plasmids were analyzed by conjugation, S1-PFGE, Southern blotting and PCR-based replicon typing (PBRT). The genetic environment of the bla (KPC-2) gene was determined using PCR and sequencing. PCR analyses revealed that the E1 isolate carried the bla (KPC-2), bla (CMY-2), bla (TEM-1), bla (CTX-M-14), and qnrB2 genes and belonged to sequence type ST410, phylogenetic type A; the E2 isolate was assigned to ST131-B2 and carried the bla (KPC-2), bla (TEM-1), bla (CTX-M-3), bla (DHA-1), aac(6')-Ib-cr, and qnrS1 genes; while the E3 isolate was of ST648-D and possessed bla (KPC-2), bla (TEM-1), bla (OXA-1), bla (CTX-M-15), armA, and aac(6')-Ib-cr genes. PFGE demonstrated that each of the three KPC-2-producing E. coli isolates exhibited an individual XbaI patterns. The bla (KPC-2) gene was located on plasmids of 60-140 kb with IncA/C, IncN, or non-typeable replicon types. The genetic environment of bla (KPC-2) of the three strains was consistent with the genetic structure of bla (KPC-2) on the plasmid pKP048.