Comparative evaluation of phenotypic tests for identification of Extended Spectrum Beta Lactamases (ESBL) and Metallo-Beta-Lactamases(MBL) producing Pseudomonas aeruginosa from pus samples of hospitalized patients of tertiary care hospital, one year study

Abstract

Background: Pseudomonas aeruginosa is one of the most common pathogens causing nosocomial infection mainly causing wound infections and an opportunistic pathogen with physiologically versatile nature. It flourishes as a saprophyte, with innate resistance to many antibiotics and disinfectants. In addition to its innate resistance, acquired resistance is particularly associated with indiscriminate antibiotic use. ESBL and MBL production are important examples of them. With worldwide increase in occurrence and rate of dissemination of ESBL and MBLs, early detection is essential. This will help in timely implication of strict infection control practices as well as clinical guidance regarding potential risk of therapeutic failure. Aim of the Study: The present study was undertaken 1. To compare different phenotypic tests for identification of ESBL and MBL producing P.aeruginosa from pus samples received at microbiology department. 2. To know the prevalence of ESBL and MBL producing P.aeruginosa isolated from pus samples. Materials and Methods: The present study was undertaken at the Department of Microbiology, J.N.Medical College, Belgaum during the period from Jan 2011 to Dec 2011. All the P.aeruginosa isolated from 1200 pus samples in hospitalized patients of K.L.E.’S DR. Prabhakar Kore Hospital and MRC, Belgaum, received at Microbiology department were included in the study. Isolates showing resistance to Ceftazidime were selected for detection of ESBL enzyme by Double Disc Synergy Test and Disc Diffusion Test. Isolates showing resistance to Imipenem were selected for detection of MBL enzyme by Imipenem ( IMP ) - EDTA Combined Disc Test, Imipenem ( IMP ) - IV EDTA double disc Synergy Test, EDTA disc potentiation using Ceftazidime, Ceftizoxime and Cefotaxime and Modified Hodge test . Results: Out of the 90 P.aeruginosa isolated from 1200 pus samples, 57 ( 63% ) were Cefazidime sensitive and 33( 37% ) were resistant. Of the 33 P.aeruginosa resistant to Ceftazidime, Disc Diffusion Test detected 9 ( 27% ) of ESBL producers and Double Disc Synergy Test detected 17( 51% ) . And out of the 90 P.aeruginosa isolated from 1200 pus samples, 66( 73.3% ) were Imipenem sensitive and 24( 26.6% ) were resistant. Of the 24 P.aeruginosa resistant to Imipenem, IMP-EDTA CDT detected 14( 58% ) of ESBL producers, IMP- EDTA DDST detected 7( 29% ) , EDTA disc potentiation test detected 11( 46% ) and Modified Hodge method detected 8( 33% ) . Conclusion: This study showed that Double Disc Synergy Test is a better method to detect ESBL producers and IMP-EDTA Combined Disc Test for detection of MBL producing P.aeruginosa.