Comparison of various phenotypic tests for detection of metallo-beta-lactamase in Pseudomonas aeruginosa isolates at a Tertiary care centre

Introduction: Pseudomonas aeruginosa is an opportunist pathogen, aerobic Gram negative bacilli belonging to family Pseudomonodaceae and genus Pseudomonas. Aim of the study is to compare of various phenotypic tests for detection of metallo-β-lactamase (MBL) in Pseudomonas aeruginosa. Objectives of the study: 1. Isolation and identification of P.aeruginosa from various clinical samples. 2. To determine the prevalence of metallo-β-lactamase in clinical isolates of Pseudomonas aeruginosa. 3. Comparison of different phenotypic tests for MBL detection. Materials and Methods: Pseudomonas aeruginosa isolates were isolated from various clinical samples for a period of one year from January 2016 to December 2016 at Shri B M Patil medical college hospital and research Centre. Samples which yielded P. aeruginosa were included in the study. Isolates resistant to imipenem were tested for MBL production using following three phenotypic tests 1. Double disk synergy test (DDST) (imipenem, EDTA 750μg/ml) 2. Combined disk test (CDT) (imipenem, imipenem + EDTA 750μg/ml) 3. MBL E test strip (Hi media) Results: A total of 92 P. aeruginosa were isolated. Of these, 22 were resistant to Imipenem and these were subjected to the phenotypic tests. MBL E test strip identified 13 (59%), CDT identified 10 (45.4%) and DDST identified 5 (22.7%) isolates as MBL producers. Majority of MBL producing isolates were isolated from pus sample. More isolates were obtained from in-patients compared to out-patients. Conclusion: Prevalence of MBL producing P. aeruginosa is 14%. MBL E test strip detected highest number of MBL producing isolates.