Laboratory Detection of Carbapenemase-Producing Enterobacterales: Phenotypic and Molecular Approaches - A Narrative Review

Background: Carbapenem-resistant Enterobacterales (CRE) are a critical-priority pathogen group on the World Health Organization's 2024 list. Most clinically significant carbapenem resistance in Enterobacterales is mediated by acquired carbapenemases, chiefly KPC, NDM, VIM, IMP and OXA-48- like enzymes. Accurate and timely laboratory detection of these enzymes directly shapes antimicrobial therapy, infection prevention and surveillance. Aim: To review the phenotypic, immunochromatographic, molecular and mass-spectrometric methods available to clinical laboratories for detecting carbapenemase-producing Enterobacterales (CPE), and to propose a practical, tiered testing algorithm. Review Results: The CLSI-endorsed modified carbapenem inactivation method (mCIM) offers sensitivity of about 97–99% and specificity of 99–100% at a reagent cost near one US dollar, but needs an overnight incubation. When paired with the EDTA-modified method (eCIM), it also separates metallo-β-lactamases from serine carbapenemases. Colorimetric tests such as Carba NP give results within about 2 hours but miss a proportion of OXA-48-like producers. Multiplex lateral flow immunoassays identify the five major enzyme families in about 15 minutes with reported sensitivity and specificity above 95%. Real-time PCR platforms such as Xpert Carba-R deliver gene-level results within about an hour but detect only targeted genes. Conclusion: No single method is sufficient for every laboratory. A tiered approach that screens with a low-cost phenotypic test, classifies the enzyme with an immunochromatographic or molecular assay, and refers discordant isolates for sequencing gives the best balance of accuracy, speed and cost.