NDM

NDM, short for New Delhi metallo-beta-lactamase, refers to a family of zinc-dependent enzymes that confer resistance to beta-lactam antibiotics, including carbapenems. NDM enzymes are Ambler class B metallo-beta-lactamases that hydrolyze the beta-lactam ring, rendering many antibiotics ineffective.

The bla_NDM gene family is typically carried on plasmids, enabling rapid horizontal transfer among Gram-negative bacteria such as Klebsiella pneumoniae and Escherichia coli. First identified in 2008 in a patient treated in New Delhi, NDM has since been detected worldwide and is associated with outbreaks in healthcare settings as well as community contexts.

NDM producers commonly harbor additional resistance determinants, which can broaden resistance to other antibiotic classes. The phenotype often shows resistance to carbapenems, severely limiting treatment options. Aztreonam is intrinsically less susceptible to hydrolysis by MBLs like NDM, but many NDM producers also carry other beta-lactamases that hydrolyze aztreonam; thus combining aztreonam with beta-lactamase inhibitors such as avibactam or other newer inhibitors is an area of clinical interest. Treatment of infections caused by NDM-producing bacteria typically relies on non-beta-lactam agents (e.g., polymyxins, tigecycline, fosfomycin) and, in some cases, combination or novel beta-lactam/beta-lactamase inhibitor therapies.

Public health responses emphasize rapid detection, infection control, and antimicrobial stewardship to limit spread. Diagnostics include molecular methods to detect bla_NDM genes and phenotypic tests to infer MBL activity. Ongoing research aims to develop effective metallo-beta-lactamase inhibitors and expand therapeutic options.

Variants of bla_NDM (such as NDM-1, NDM-2, etc.) have been described, with ongoing surveillance to monitor emergence and regional distribution.