Characterization of an New Delhi-Metallo-1–Producing Enterobacter cloacae ST418 Strain from a Patient in Guangzhou,China

Abstract

New Delhi-Metallo-1–producing (NDM-1–producing) Enterobacter cloacae is one of the highly resistant pathogens affecting the intensive care unit. A previous study reported that ST418 was the main epidemic type of NDM-1–producing E. cloacae in Shenzhen, China. However, few NDM-1–producing carbapenem-resistant Enterobacter cloacae ST418 strains have been described. In this study, we collected and characterized an NDM-1–producing carbapenem-resistant E. cloacae strain, E70, from a patient in Guangzhou. E70 was resistant to multiple antibiotics, including imipenem and meropenem. S1-Pulsed field gel electrophoresis and southern blotting showed that E70 harbored four plasmids and that the bla_NDM-1 gene was located on an ∼50 kb plasmid. Conjugation experiments revealed that the two smaller plasmids were transferable and that transconjugants obtaining one or both plasmids acquired different antimicrobial resistances. Whole-genome sequencing and analysis revealed that E70 belonged to ST418. The bla_NDM-1 and bla_SHV-12 genes coexisted on the 53.7 kb IncX3 plasmid pE70-NDM1, whereas the bla_CTX-M-3 and bla_TEM-1 genes were located on another untyped 26.0 kb plasmid, pE70-TEM1. The bla_NDM-1 plasmids in Enterobacter cloacae ST418 may serve as an important vehicle in the dissemination of NDM, and the coexistence of transferable plasmids increases the possibility of rapid horizontal spread of multidrug resistance genes. Long-term monitoring and detailed study are necessary for the prevention of bla_NDM-1-carrying E. cloacae infection.