Evaluation of Disk Potentiation Test (DPT) and Double Disk Synergy Test (DDST) for The Detection of Metallo-β-lactamases (MBLs) in Clinical Isolates of Bangladesh

Abstract

Objective: Increasing the emergence of Metallo-β-lactamase (MBL) producing gram-negative Enterobacteriaceae and their dexterous horizontal transmission of the gene among other strains, demands rapid and accurate detection. This study was conducted to determine a suitable MBL detection method that could promptly identify the distribution of MBL-producing Gram-negative isolates at hospital settings in Bangladesh. Methods: A total of 103 gram-negative bacilli were identified from various clinical samples at a tertiary care hospital in Dhaka city. MBL producers were detected by two phenotypic methods; Disk Potentiation Test (DPT) and the Double Disk Synergy Test (DDST) based on β-lactam chelator combinations where EDTA/SMA has been used as inhibitor and Imipenem, Ceftazidime as substrates. Results: All 103 isolates which were identified as Escherichia coli spp, Klebsiella spp, Pseudomonas spp, Acinetobacter spp, Proteus spp, Providencia spp were found to be multidrug-resistant in antibiogram test. All the mentioned isolates showed complete resistance (100%) to Imipenem, Meropenem, and Amoxiclav. The highest carbapenem-resistant etiological agents isolated were Acinetobacter spp 40 (38.8%) followed by Pseudomonas spp 27 (26.2%), Klebsiella spp 26 (25.2%), Escherichia coli 8(7.8%), Proteus spp 1(1%) and Providencia spp 1(1%). DPT method detected significantly (p=0.000009) higher number of MBL-producers (n=61, 59.2% & n=56, 54.4%) compared to the DDST method (n=43, 41.7%, n=38, 36.9% & n=15, 14.6%). Conclusion: This study depicts that DPT is a more sensitive method than DDST and could be recommended for identifying MBL-producing bacteria in Bangladeshi hospitals for the proper management of patients, and to reduce time constraints as well as treatment costs.