Incidence of metallo beta lactamase producing Pseudomonas aeruginosa in ICU patients

Abstract

Background & objective: Metallo beta lactamase (MBL) producing Pseudomonas aeruginosa have been reported to be important cause of nosocomial infections. The appearance of MBL genes and their spread among bacterial pathogens is a matter of concern with regard to the future of antimicrobial therapy. The present study was undertaken to determine the incidence of MBL producing P. aeruginosa in patients with diabetes and cancer admitted to the intensive care unit of a tertiary care hospital in western India and to assess the clinical outcome after antimicrobial treatment.

Methods: A total of 240 isolates of P. aeruginosa from various specimens between January and December 2005 were subjected to susceptibility testing against various antibiotics by disc diffusion test as per the Clinical and Laboratory Standards Institute (CLSI) guidelines. Imipenem and meropenem resistant isolates were selected for the detection of MBL production by disc potentiation test. Enhancement of inhibition zone around imipenem and meropenem discs impregnated with EDTA as compared to those without EDTA confirmed MBL production.

Results: Of the 240 P. aeruginosa isolates, 60 (25%) were found to be carbapenem resistant and 50 (20.8%) were found to be MBL producers. Of the 50 MBL producing isolates, 38 (76%) were from diabetes patients and 12 (24%) from cancer patients. Overall, 36 per cent patients responded to gatifloxacin, 42 per cent responded to piperacillin/tazobactam while 14 per cent responded to combination of gatifloxacin and piperacillin/tazobactum. Due to this nosocomial pathogen, the average hospital stay was 32 days and was associated with 20 per cent mortality due to septicaemia.

Interpretation & conclusion: Our findings showed that there is a need to do surveillance to detect MBL producers, judiciously use carbapenems to prevent their spread and use effective antibiotics, such as gatifloxacin and piperacillin-tazobactum, after sensitivity testing for treatment.