Metallo betalactamase (MBL) mediated resistance to carbapenems is an emerging threat in nosocomial infections caused by Pseudomonas aeruginosa. MBLs hydrolyze virtually all beta-lactam antibiotics leaving clinicians with no options for treatment, except Aztreonam and Polymyxin B. Very limited data available on impact of MBL producing Pseudomonas aeruginosa infections on mortality necessitated the present study. Of the 523 patients presenting with P. aeruginosa, 110 isolates from nosocomial infections (as per CDC definitions) were subjected to MBL detection by IMIPENEM+EDTA combined disc test. Incidence of Imipenem resistant Metallo betalactamase positive P.aenigmosa(IR-MBLP-PA) and Metallo-beta-lacatamse negative P. aeruginosa(MBLN-PA) infections was 21.82% and 9.38% respectively (P value 0.01 S) with six distinct antibiogram types circulating in the hospital. Mean duration of stay in the hospital before the isolation was 22±13.5 days. Overall mortality in P. aeruginosa infections was 13.63% (15/110). Increased mortality was observed in IR-MBLP-PA than in MBLN-PA (42.68% Vs 9.37% P value=0.01 S) with a mean duration of stay in ICU till death of 3.16±0.98 days indicating the severity of the infections. All deaths among IR-MBLP-PA infections were due to VAP as an underlying disease. Previous Imipenem therapy was significantly associated with IR-MBLP-PA infections (P value <0.001 HS) resulting in emergence and/or acquisition of IR-MBLP-PA. Other predisposing risk factors were significantly associated with IR-MBLP-PA infections. IR-MBLP-PA infections results in higher mortality than IR-MBLN-PA. VAP is the underlying disease in majority of deaths due to IR-MBLP-PA infections. Attributable mortality in IR-MBLP-PA infections, is partially mediated by production of Metallo-betalactamases, severity of underlying disease, predisposing risk factors, Multidrug resistance and Pan drug resistance, making IR-MBLP-PA isolate, a nosocomially successful and difficult to treat pathogen. Patients in whom Imipenem is selected as antipseudomonal antibiotic, the potential for emergence of IR-MBLP-PA strains should be anticipated, and in appropriate circumstance, routine culture and screening for MBL production should be performed to detect the emergence of IR-MBLP-PA strains. These findings can be generalized to other tertiary care hospitals with similar conditions. Further studies are needed to explore the population dynamics, virulence factors, an effective antibiotic and expression of MBL production in vivo of this serious pathogen. © 2012 Elsevier B.V., All rights reserved.