Incorporating Detection of Carbapenem Resistant Enterobacterales by Modified Carbapenem Inactivation Method (mCIM) and EDTA Carbapenem Inactivation Method (eCIM) in Surveillance Protocol, to Rationalize Antibiotic Therapy

Authors

Keywords:

Carbapenem-Resistant Enterobacterales, Carbapenemases, Metallo-Beta-Lactamases, Antimicrobial Resistance, Polymerase Chain Reaction

Abstract

Background

Carbapenem-resistant Enterobacterales (CRE) are an emerging global public health threat associated with multidrug resistance, prolonged hospitalization, increased healthcare costs, and elevated mortality. Early identification of carbapenemase mechanisms is essential for effective antimicrobial therapy, infection-control practices, and antimicrobial stewardship. Differentiation between metallo-β-lactamase (MBL) and serine β-lactamase (SBL) producers is clinically important because SBL-producing isolates may respond to ceftazidime-avibactam, whereas MBL-producing isolates often require combination therapy with ceftazidime-avibactam and aztreonam. Modified carbapenem inactivation method (mCIM) and EDTA-carbapenem inactivation method (eCIM) are economical phenotypic assays that can reliably detect and differentiate carbapenemase-producing Enterobacterales. This study aimed to incorporate mCIM and eCIM into surveillance protocols for characterization of CRE isolates and rationalization of antibiotic therapy.

 

Methods

This retrospective cross-sectional study included 45 archived multidrug-resistant Enterobacterales isolates resistant to carbapenems, obtained from urine, blood, exudates, tissue, wound swabs, and sterile body fluids. Isolates were revived and identified using standard biochemical tests. Carbapenemase production was screened using mCIM and differentiated into metallo-β-lactamase (MBL) and serine β-lactamase (SBL) producers using eCIM according to CLSI 2023 guidelines. Real-time PCR was performed for detection of blaNDM-1, blaOXA-48, blaKPC, blaIMP, and blaVIM genes.

 

Results

Among the 45 isolates studied, Klebsiella pneumoniae (62%) and Escherichia coli (34%) were the predominant organisms. Phenotypic testing showed 36 (80%) isolates as MBL producers, 5 (11%) as SBL producers, and 4 (9%) negative for carbapenemase production. RT-PCR detected blaNDM-1 in 36 isolates and blaOXA-48 in 5 isolates, while blaKPC, blaIMP, and blaVIM were not detected. Co-expression of blaNDM-1 and blaOXA-48 was observed in 22 isolates. Most isolates demonstrated high resistance to β-lactams and fluoroquinolones, while tigecycline and minocycline retained comparatively better activity. Majority of patients recovered, with an overall mortality rate of 13%.

References

1. Pierce VM, Simner PJ, Lonsway DR, Roe-Carpenter DE, Johnson JK, Brasso WB, et al. Modified Carbapenem Inactivation Method for Phenotypic Detection of Carbapenemase Production among Enterobacteriaceae. J Clin Microbiol. 2017;55:2321–33.

2. Sfeir MM, Hayden JA, Fauntleroy KA, Mazur C, Johnson JK, Simner PJ, et al. EDTA-Modified Carbapenem Inactivation Method: a Phenotypic Method for Detecting Metallo-β-Lactamase-Producing Enterobacteriaceae. J Clin Microbiol. 2019;57:e01757-18.

3. Tsai YM, Wang S, Chiu HC, Kao CY, Wen LL. Combination of modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) for phenotypic detection of carbapenemase-producing Enterobacteriaceae. BMC Microbiol. 2020;20:315.

4. Kumarasamy KK, Toleman MA, Walsh TR, Bagaria J, Butt F, Balakrishnan R, et al. Emergence of a new antibiotic resistance mechanism in India, Pakistan, and the UK: a molecular, biological, and epidemiological study. Lancet Infect Dis. 2010;10:597–602.

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Published

2026-08-19

How to Cite

Murugan, H., Devi C, S., & D, S. (2026). Incorporating Detection of Carbapenem Resistant Enterobacterales by Modified Carbapenem Inactivation Method (mCIM) and EDTA Carbapenem Inactivation Method (eCIM) in Surveillance Protocol, to Rationalize Antibiotic Therapy . International Journal of Medical Students. Retrieved from https://ijms.pitt.edu/IJMS/article/view/4880

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Forthcoming

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Abstracts of the WCMSR

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Copyright (c) 2026 Harinee Murugan, Sheela Devi C, Sridevi D

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