Molecular characterization of metallo-beta-lactamase producers among carbapenem resistant Pseudomonas aeruginosa isolated from cases of hospital acquired infections in a tertiary care hospital, Bengaluru

Abstract

: Pseudomonas aeruginosa is an important cause of multidrug-resistant nosocomial infections. The knowledge of resistance mechanisms in Pseudomonas is an important issue for antimicrobial treatment. Therefore, the objective was to detect carbapenems resistance in P. aeruginosa by phenotypic methods and genes (blaIMP and blaVIM) coding for carbapenemase resistance.The study conducted in the Department of Microbiology, BMCRI, Bengaluru. 91 samples from the patients hospitalised for 48 hours and more were processed. Carbapenem resistant P. aeruginosa (CRPA) were identified by biochemical tests and by Kirby Bauer Disk diffusion method as per CLSI guidelines. Those carbapenem resistant isolates were further subjected to two MBL detecting phenotypic tests- Modified Hodge Test (MHT) and Combined disk Test (CDT) by using imipenem and imipenem/ EDTA disk and MBL genes (blaIMP and blaVIM) were identified by PCR.91 clinical isolates were identified as CRPA, 92.3% isolates were positive by CDT whereas only 13.2% of isolates showed positive by MHT method indicating MBL production. Among 91 strains, 19.04% strains were harbouring blaVIM and 1.2% strain harbouring blaIMP gene.The detection of MBL-producing P. aeruginosa help in appropriate antimicrobial therapy and avoid development and dissemination of these strains. Hence routine detection of MBL production in P. aeruginosa should be undertaken. All CRPA isolates should be routinely screened for MBL production using CDT and positive isolates should be confirmed by PCR. MHT test had low sensitivity. To understand the epidemiology, there is a need of genetic analysis and typing of MBL enzymes.