Genetic features of blaNDM-1-positive Enterobacteriaceae.

Genetic features associated with the bla(NDM-1) gene were investigated in 6 Escherichia coli, 7 Klebsiella pneumoniae, 1 Citrobacter freundii, 1 Proteus mirabilis, and 1 Providencia stuartii isolate of worldwide origin. Clonal diversity was observed for both E. coli and K. pneumoniae. The bla(NDM-1) gene was carried by different plasmid types (IncA/C, IncF, IncL/M, or untypeable) and was likely chromosome borne in two isolates. The bla(NDM-1) plasmids coharbored a variety of resistance determinants, including β-lactamase genes, quinolone resistance genes, and 16S RNA methylase genes.