Status of Metallo-β-Lactamase-Producing Organisms in Clinical Samples

Introduction: Carbapenem resistance, due to the production of carbapenemase enzymes in various bacteria, is responsible for numerous outbreaks and is significantly associated with healthcare-associated infections.Metallo--lactamases (MBLs) are carbapenemases that hydrolyze all -lactam antibiotics except monobactams.The most prominent bacteria exhibiting this resistance mechanism include members of the Enterobacteriaceae family and Pseudomonas aeruginosa.Therefore, this study aims to assess the prevalence of MBL production among Gramnegative bacteria at Kirtipur Hospital.Methods: This study was conducted at Kirtipur Hospital from June 26, 2022, to September 28, 2022.Organisms were isolated and identified from clinical samples including urine, blood, wound swabs, sputum, tissues, pus, catheter tips, and other body fluids, following standard laboratory protocols.Carbapenemase production was detected using the modified Carbapenem Inactivation Method (mCIM), with metallo--lactamase (MBL) production confirmed by the EDTA-modified Carbapenem Inactivation Method (eCIM) test.Results were interpreted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, M100, 31st ed., 2021.Results: From 1988 clinical samples, 388 Gram-negative bacteria were isolated, with Escherichia coli, Klebsiella pneumoniae, and P. aeruginosa being the predominant species.Antibiotic susceptibility testing revealed that Amikacin was the most effective against Enterobacteriaceae, exhibiting a susceptibility rate of 84.05%.In contrast, Cefepime was the most effective against non-Enterobacteriaceae Gramnegative bacteria with susceptibility rate of 60%.Screening identified 23.40% (84/359) of isolates as potential carbapenemase producers, with 15.32% (55/359) confirmed as carbapenemase producers via mCIM.Of these, 56.36% (31/55) were MBL producers, representing 8.63% (31/359) of all screened isolates.Among confirmed carbapenemase producers, P. aeruginosa exhibited the highest MBL production rate at 77.78% (7/9 isolates), followed by K. pneumoniae at 73.68% (14/19), E. coli at 41.18% (7/17), C. koseri at 33.33% (2/6), and P. mirabilis at 25% (1/4).Conclusion: This study underscores the significant threat posed by MBL-producing E. coli, K. pneumoniae, and P. aeruginosa in this healthcare setting.Therefore, implementing routine screening for MBL-producing organisms in diagnostic laboratories is crucial for controlling the spread among hospital patients and guiding effective antibiotic therapy.