Occurrence of Carbapenem Resistant Gram Negative Bacteria by Using Modified Carbapenem Inactivation Method

Background: The rapid emergence of carbapenem-resistant Gram-negative bacteria has become a major concern in healthcare institutions worldwide. Carbapenems are considered the drugs of choice for severe infections caused by multidrug-resistant organisms however, increasing resistance has significantly compromised their effectiveness. The aim is to determine the occurrence of carbapenemase-producing Gram-negative bacteria among clinical isolates and characterize carbapenemase types using phenotypic methods. Material and Methods: An observational study was conducted in the Department of Microbiology, Teerthankar Mahaveer hospital. A total of 209 Gram-negative bacterial isolates recovered from various clinical specimens were included. Carbapenemase production was detected by Carbapenem inactivation methods (CIM) including modified CIM (mCIM) and EDTA CIM (eCIM) to identify metallo-β-lactamases (MBLs) and serine carbapenemases as per Clinical laboratory standards institute (CLSI) standards, M100 2025. Results: Among 209 isolates, 66 (31.6%) were confirmed as carbapenemase producers. Male patients constituted 56.06% of positive cases, while females represented 43.94%. The highest frequency was observed in the 61-80 year age group. Intensive care units (ICUs) accounted for majority of carbapenemase-producing isolates particularly the Medical Intensive Care Unit (MICU). Escherichia coli was the most common organism (43.9%) followed by Klebsiella pneumoniae (31.8%) and Pseudomonas aeruginosa (24.2%). Of the 66 carbapenemase producers 42 (63.6%) were Metallo-beta-lactamase (MBL) producers and 24 (36.4%) were serine carbapenemase producers. Conclusion: A considerable occurrence of carbapenemase-producing Gram-negative bacteria was identified in hospitalized patients, particularly in critical care settings. Phenotypic methods such as mCIM and eCIM provide reliable and affordable tools for routine detection and classification of carbapenemases, facilitating timely infection control interventions.

Keywords: Carbapenem resistance, Carbapenemase, mCIM, eCIM and antimicrobial resistance.