Evaluation of Three Phenotypic Methods for Detecting Metallo-β-Lactamase in Clinical Isolates of Acinetobacter...

Background Carbapenem resistance mediated by metallo-β-lactamase (MBL) production in Acinetobacter baumannii represents a growing global health threat. Early detection of MBL-producing organisms is essential for the prompt administration of appropriate therapy to effectively manage infections. Materials and methods This cross-sectional study was conducted in the Department of Microbiology, Index Medical College Hospital and Research Centre (IMCHRC), Indore, from October 2019 to September 2021. A. baumannii strains showing resistance or intermediate susceptibility to imipenem and meropenem were subjected to MBL detection using phenotypic methods, namely the Modified Hodge Test (MHT), Double-Disk Synergy Test (DDST), and MBL E-test. Results Out of 143 clinical isolates of A. baumannii, 132 isolates were resistant to carbapenems across various clinical specimens. Among these 132 carbapenem-resistant A. baumannii (CRAB) isolates, MBL production was detected in 132 (100%) by the E-test, 126 (95.45%) by MHT, and 120 (90.9%) by DDST. Six isolates (4.54%) were negative by MHT, and 12 isolates (9.1%) were negative by DDST. Sensitivity and specificity of the phenotypic methods were analyzed using the MBL E-test as the gold standard for detecting MBL production in CRAB isolates. Conclusions Clinical isolates of A. baumannii producing MBL should be routinely screened in diagnostic laboratories to help control resistance and guide therapy, as MBL production is associated with multidrug resistance and confers resistance to carbapenems, which are reserved for severe infections. Among the phenotypic methods, the MBL E-test demonstrated superior accuracy compared to MHT and DDST for detecting MBL-producing A. baumannii isolates.