Identification of a novel blandm variant, blandm-33, in an escherichia coli isolate from hospital wastewater in china

Since the discovery of NDM-1 and the worldwide reporting of different variants have raised alarms concerning global health, the problem of carbapenem-resistant Enterobacterales (CRE) has become increasingly serious. Therefore, research on the hydrolytic activity and molecular structure of NDM variants is beneficial to the development of antibacterial drugs. NDM has been evolving into variants that possess different hydrolysis activities toward b-lactam antibiotics. Here, we characterized a novel blaNDM variant, named blaNDM-33, identified from a multidrug-resistant Escherichia coli strain from hospital sewage. NDM-33 differed from NDM-5 with a single-aminoacid substitution (A72T). blaNDM-5 was located in the Tn125-related blaNDM-33 region from an IncX3-type plasmid, pHD6415-NDM, that can be transferred horizontally. The genetic construct of blaNDM-33 showed higher MICs of carbapenems than a blaNDM-5 construct. Enzyme kinetics showed that NDM-33 had higher enzymatic activity for meropenem and cefazolin than NDM-5. The emergence of this novel NDM variant could pose a threat to public health because of its transferability and enhanced carbapenem activity.