A Study on Metallo-beta-lactamase Mediated Resistance in Clinical Isolates of Pseudomonas aeruginosa

The emergence of MBL as a mode of carbapenem resistance has proved a global threat due to its broad spectrum of activity and rapid rate of dissemination. MBL producing Pseudomonas aeruginosa strains are responsible for several nosocomial outbreaks in tertiary care centers across the world. This study was undertaken to determine the prevalence of MBL among clinical isolates of Pseudomonas aeruginosa in a tertiary care hospital and to determine their antibiotic susceptibility pattern. 143 clinical isolates of Pseudomonas aeruginosa were obtained over a period of 1 year from December 2012 to November 2013 at Sree Gokulam Medical College and Research Foundation, Venjaramoodu, Trivandrum. Their antibiotic susceptibility pattern was determined by Kirby Bauer disc diffusion method as per CLSI guidelines. The carbapenem resistant strains were screened for MBL production by Imipenem-EDTA Combined disc test. MBL E-test was used for confirmation of MBL production 47 (32.87%) out of 143 isolates showed resistance to carbapenems. Among these, 20 were positive for MBL production by the combined disc test. Of these, 19 isolates were positive for MBL production by E-test. Prevalence of MBL among Pseudomonas aeruginosa was thus found to be 13.3%. The MBL producing strains showed almost complete resistance to beta-lactams (except aztreonam), aminoglycosides and fluoroquinolones. Colistin was found to be 100% sensitive and hence may prove a possible therapeutic option.