Evaluation of simplified carbapenem inactivation method (sCIM) as a phenotypic method for rapid detection of carbapenemase-producing Enterobacterales: Study from a tertiary care hospital in North India

Objectives: This study aims to assess the feasibility of using the simplified carbapenem inactivation method (sCIM) for detecting carbapenemase production, specifically comparing its efficacy with the modified carbapenem inactivation method (mCIM), emphasizing methods applicable in low-resource settings and a minimal learning curve. Materials and Methods: To evaluate the performance of sCIM, 102 clinical isolates of carbapenem-resistant Enterobacterales (CREs) (detected by Kirby–Bauer disk diffusion technique) were selected, which had previously undergone both mCIM testing and genotyping detection of common carbapenemase-encoding genes. Polymerase chain reaction analysis of the isolates was done with specific primers targeting carbapenemase genes (blaNDM, blaIMP, blaVIM, blaSPM, blaKPC, and blaOXA48). Statistical analysis: Data were analyzed using the Statistical Package for the Social Sciences v.23. Quantitative variables were described using mean ± standard deviation or median (interquartile range). Categorical variables were described using proportions. Results: The sensitivity of sCIM was 90.43%, with a specificity of 87.5% when compared to the mCIM. The organism-wise analysis revealed notable sensitivity rates for Escherichia coli (93.44%) and Klebsiella pneumoniae (84.38%). Highlighting the efficacy of sCIM in identifying carbapenemase production in them. The specificity for sCIM remained high across all species, with 100% specificity for E. coli and 80% specificity for K. pneumoniae . Conclusions: The findings of our study support the efficacy of sCIM as a sensitive and specific method for the rapid detection of carbapenemase-producing CRE. The simplification of procedures and improved detection capabilities make sCIM a promising tool for timely and accurate identification, offering advantages over the traditional mCIM.