New Delhi metallo-β-lactamase (NDM) is an enzyme and readily transferable antibiotic resistance factor that can spread from one strain of bacteria to another by horizontal gene transfer. NDM confers enteric bacteria resistance to nearly all β-lactams, including carbapenems, which are a mainstay for the treatment of antibiotic-resistant bacterial infections. NDM-1 was initially identified from Klebsiella pneumoniae in 2008 and since then 17 new NDM alleles have been identified (NDM-1 to -17), with most of them originating from Asia. The variants arise from site mutations within the gene encoding the beta-lactamase. NDM-1 is the most common variant in cases of clinical infections. Accurately diagnosing NDM is crucial for effective treatment and preventing the spread of antibiotic-resistant bacteria.