Since metallo-b-lactamases can inactivate the b-lactam antibiotic drugs by cleaving the amide (carbon-nitrogen) bond of the blactam ring [2] , it can provide us very useful insights about the essence of the drug resistance problem by analyzing the binding interaction modes obtained by docking Imipenem and Meropenem to NDM-1 receptor, respectively. Shown in Fig. 3B is a close view of the binding interactions obtained by docking the antibiotic drug Imipenem to the receptor NDM-1. Its binding pocket is formed by nine residues that have at least one heavy atom with a distance within 5 Å [55] to Imipenem, as labeled in Fig. 3B . Interestingly, the constituent residues thus defined for the binding pocket are quite consistent those identified by the online web-server tool Q-SiteFinder for forming the extended cleft active site of NDM-1. In the NDM-1/Imipenem complex, Met3 and Phe6 are located on the brink of the active site, providing some van der Waals interactions to the drug molecule. It can be seen from Fig. 3B that, in addition to the van der Waals interaction of the Imipenem drug with the surrounding binding pocket residues, there are remarkable hydrogen bonds that have tightly tethered the drug to Glu88 and Thr126 of the receptor, making NDM-1 able to recognize the antibiotic drug followed by cleaving the amide bond of its b-lactam ring so as to inactivate Imipenem. The detailed information for these hydrogen bonds is listed in Table 1 .