Detection of metallo-beta-lactamase (MBL) producing Pseudomonas aeruginosa at a tertiary care hospital in Kashmir

Abstract

Metallo-beta-lactamases (MBL) producing Pseudomonas aeruginosa strains are responsible for several nosocomial outbreaks in tertiary care centers across the world. It is well known that poor outcome occurs when patients with serious infections due to MBL producing organisms are treated with antibiotics to which the organism is completely resistant. Therefore, detection of these MBL producing P. aeruginosa is crucial for optimal treatment of critically ill patient’s and to prevent the spread of resistance. Current study was undertaken with the aim of optimizing the choice, dose and duration in MBL producingP. aeruginosa infections in a tertiary care center in Kashmir for various types of treatment modalities. Aims and objectives are now specific and not like introduction. Various clinical samples were obtained from patients admitted in hospital or attending the OPD between January 2007 to June 2008. Antimicrobial sensitivity was performed by Kirby-Bauer disk diffusion method. Minimum inhibitory concentration (MIC) of Imipenem resistant isolates was done by agar dilution method. Metallo-beta-lactamase production was detected by combined disk method, MIC reduction of imipenem in presence of EDTA and by Epsilometer test (E-test). The intergroup comparison and risk estimation was performed by using Fisher’s exact test and Odd’s ratio. Out of 283 P. aeruginosa isolates, 38 (13.42%) were resistant to Imipenem. Thirty three (11.66%) were found to be MBL producers by combined disk test and all of them showed reduction in MIC in the presence of imipenem-EDTA in E-test. The number of MBL positive isolates from ICU was statistically significant (p=0.027). The hospital stay was significantly longer (p=0.000) among patients infected with MBL producers than MBL non producers. Statistically significant association of antineoplastic chemotherapy, urinary catherization with MBL production was found. All MBL producers were resistant to commonly used antibiotics. However, they were sensitive to polymyxin B(100%), piperacillin/tazobactum (18.2%), amikacin and ciprofloxacin (9.1%). MIC reduction is a cumbersome, laborious method and given the cost constraints of E-test a simple screening test like combined disk test may be used. In absence of therapeutic MBL inhibitors, polymyxins, aminoglycoside or fluoroquinolone molecule that may have retained some activity against the isolate may be used for the treatment of MDR P. aeruginosa infections. Key words: Pseudomonas aeruginosa, combined disc test, Epsilometer test, Metallo-beta-lactamase.