Year: 2026 | Month: October | Volume: 16 | Issue: 10 | Pages: 8-16
DOI: https://doi.org/10.52403/ijhsr.20261002
Screening for Carbapenemase Production in Gram Negative Bacilli: A Phenotypic Study in a Tertiary Care Hospital
Jani V1, Chaudhary A2, Solanki R3
1Senior Resident, 3Junior Resident, 3Professor,
Department of Microbiology, Dr. M.K. Shah Medical College and Research Centre, Gujarat University, Ahmedabad, India.
Corresponding Author: Dr. Vaibhavi Jani
ABSTRACT
Introduction: Carbapenem-resistant Gram-negative bacilli (CR-GNB) are a major global health concern due to limited therapeutic options and rapid dissemination of resistance mechanisms. Carbapenemase production is a key contributor to resistance, necessitating reliable and cost-effective detection methods.
Aim: To evaluate and compare Modified Hodge Test (MHT), Modified Carbapenem Inactivation Method (mCIM), and EDTA-modified CIM (eCIM) for detection of carbapenemase production among Gram-negative bacilli.
Materials and Methods: This prospective observational study was conducted in the Department of Microbiology of a tertiary care hospital from January to March 2026. A total of 100 non-duplicate carbapenem-resistant Gram-negative bacilli isolated from 910 clinical samples were included. Identification was performed using standard microbiological methods and VITEK 2 Compact. Antimicrobial susceptibility testing was done as per CLSI guidelines. Carbapenemase production was detected using MHT, mCIM, and eCIM. Diagnostic performance of MHT was evaluated using mCIM as the reference method.
Results: Acinetobacter spp. (37%) and Klebsiella spp. (30%) were the predominant isolates. Carbapenemase production was detected in 73% isolates by mCIM and 60% by MHT. mCIM demonstrated higher detection rates across all organisms. eCIM identified metallo-β-lactamase production in a subset of isolates. Compared to mCIM, MHT showed sensitivity of 73.97%, specificity of 77.78%, positive predictive value of 90.00%, negative predictive value of 52.50%, and diagnostic accuracy of 75.00%. Agreement between MHT and mCIM was moderate (κ=0.45). High susceptibility to colistin and tigecycline was observed.
Conclusion: mCIM is more reliable than MHT for detection of carbapenemase production, while eCIM aids in identifying metallo-β-lactamases. Early phenotypic detection is essential for appropriate therapy and infection control in resource-limited settings.
Key words: Carbapenem-resistant Gram-negative bacilli (CR-GNB), Carbapenemase, Modified Carbapenem Inactivation Method (mCIM), Modified Hodge Test (MHT), Phenotypic detection