Metallo-Betalactamase Producing Clinical Isolates of Pseudomonas aeruginosa from Intensive Care Unit Patients of a Tertiary Care Hospital

摘要

Background and Objectives: Pseudomonas aeruginosa is an important nosocomial pathogen in the health care settings. Increasing resistance to carbapenems mediated by metallo-betalactamase (MBL) and other mechanisms is a cause for concern because they adversely affect clinical outcomes and add to treatment costs. This study was undertaken to determine the prevalence of MBL production in carbapenem-resistant isolates and to study the factors influencing the clinical outcomes of infections.Materials and Methods: One hundred tweleve consecutive P. aeruginosa isolates obtained from hospitalised patients were subjected to susceptibility testing to anti-pseudomonal drugs by disc diffusion, and minimum inhibitory concentration (MIC) of imipenem was determined. The production of MBL was detected by 4-fold reduction in MIC with imipenem-ethylene diamine tetraacetic acid (EDTA) and the zone size enhancement with EDTA impregnated imipenem and ceftazidime discs.Results: By disc diffusion method, 31.2% of the P. aeruginosa isolates tested were found resistant to imipenem. 15 resistant isolates, showed a significant enhancement in zone size with the EDTA impregnated discs as well as a 4-fold reduction in MIC with imipenem EDTA. Thus 42.8% isolates of imipenem resistant Pseudomonas aeruginosa were found to be MBL producers. Overall prevalence of MBL production was 13.4% among all the Pseudomonas aeruginosa isolates.Conclusion: MBL-mediated imipenem resistance in P. aeruginosa is a cause for concern in the therapy of critically ill patients. Intensity of selection pressure for usage of broad spectrum antibiotics is high in ICUs. Therefore, a strict antibiotic policy should be followed in intensive care areas to prevent further spread of MBLs. Detection of MBLs by Disk potentiation test should be routinely performed in all microbiology laboratories for all imipenem-resistant isolates, which will help to reduce morbidity and mortality in these patients.