Worldwide distribution of NDM-1-producing E. coli and K. pneumoniae isolates. The color codes for the isolates are used to indicate the country where the isolate was recovered. Circles, E. coli; stars, K. pneumoniae. Isolates include those identified in the present study (underlined STs) and strains reported in other studies only when the results of MLST typing were available (, , –, , , ).

Schematic map of bla_NDM-1-associated genetic structures identified among enterobacterial isolates. (A) Structure identified from E. coli 271 in which the ISEc33 and ISSen4 elements have been identified on both ends of the bla_NDM-1 gene (); (B)structure in which ISAba125 is present as a truncated element, but without ISEc33 (K. pneumoniae Kp7 and 601); (C) structure in which ISAba125 is present as a full element and the ble_MBL gene is present (E. coli GUE, I5, RKI, and 5649; K. pneumoniae K2, IBN, and 419; Citrobacter freundii STE, and P. stuartii PS1); (D) structure initially identified in K. pneumoniae 05-506 (); (E) structure in which ISAba125 is present as a full element but the bleomycin resistance ble_MBL gene is absent or truncated (E. coli RIC, K. pneumoniae 6642 and 6759, Proteus mirabilis 7892). Genes and their corresponding transcription orientations are indicated by horizontal arrows. Positions of the primers as well as the bla_NDM-1 promoter are indicated.