Prevalence and Molecular Characterization of New Delhi Metallo-Beta-Lactamases in Multidrug-Resistant Pseudomonas aeruginosa and Acinetobacter baumannii from India

New Delhi metallo-beta-lactamase (NDM)-mediated carbapenem resistance in Pseudomonas aeruginosa and Acinetobacter baumannii is a major concern. We investigated the presence of NDM and its variants in P. aeruginosa and A. baumannii at a tertiary hospital in North India. A total of 236 isolates (130 P. aeruginosa and 106 A. baumannii ) were included; 38 (29.23%) P. aeruginosa and 20 A. baumannii isolates (18.8%) were resistant to carbapenems and all of them were bla NDM positive. All 38 carbapenem-resistant P. aeruginosa harbored bla NDM-1, while 12 (60%) of 20 A. baumannii harbored bla NDM-2 . Pulsed-field gel electrophoresis showed that all 58 isolates were clonally unrelated. By Southern blot analysis, bla NDM-2 was located on chromosome. The bla NDM-2 -positive isolates were more frequently recovered from tracheal aspirate (67% vs.16%; p = 0.02) and intensive care unit (67% vs. 20%; p = 0.001) than bla NDM-1 . Among other carbapenemases, VIM was significantly associated with bla NDM-1 than bla NDM-2 (61% vs. 17%; p = 0.006). Mortality between bla NDM-1 - and bla NDM-2 -infected patients was comparable. When expressed in Escherichia coli , bla NDM-2 transformant conferred one doubling dilution higher MIC value for cefotaxime, piperacillin/tazobactam than bla NDM-1 . The study shows the emergence of bla NDM- mediated resistance among P. aeruginosa and A. baumannii and rapid evolution of bla NDM-2 in A. baumannii with its chromosomal localization.