Carbapenemase detection methods for carbapenem-resistant Enterobacterales: Which to choose?

Background: Carbapenems are among the last resorts in managing multidrug-resistant bacterial infections. The rise in resistance to carbapenems is a significant concern, and the production of carbapenemases that inactivate the drug is the most typical mode of resistance developed by the bacteria. Carbapenemase-producing bacteria are associated with higher morbidity and spread faster than noncarbapenemase-producing bacteria. Detection of carbapenemases is essential for epidemiological surveillance and in choosing the most efficient antimicrobial in managing the patient. Materials and Methods: We processed urine samples received in our laboratory over 6 months. Samples with carbapenem-resistant Enterobacterales were further processed for carbapenemase detection using the modified carbapenem inactivation method (mCIM), combined disc diffusion test (CDDT), Epsilometer test (E test), and modified Hodge test (MHT). The results were analyzed. Results: A total of 32.3% of Enterobacterales uropathogens showed resistance to imipenem/meropenem. The commonest isolate was Escherichia coli, followed by Klebsiella pneumoniae. Maximum positivity was detected by mCIM (89.2%) followed by CDDT (86.5%), E test (77.1%), and MHT (54%). Conclusion: In this study, we compared four phenotypic methods of carbapenemase detection and compared their diagnostic accuracy. These included CDDT, E test, MHT, and mCIM. Maximum positivity was detected by mCIM followed by CDDT and E test.