Phenotypic and molecular methods of carbapenemase detection: Can we break the chain and preserve the carbapenems?

Background: The World Health Organization (WHO) has declared antimicrobial resistance (AMR) as one of the top ten public health threats faced by humanity. Carbapenems are currently the last option β-lactam antibiotics for treatment of both hospital and community acquired infections. The rapid rise and spread of carbapenem resistant organisms (CRO) is a global concern highlighting the need for early detection and isolation of patients.

Methods: A total of 226 non- repeat, carbapenem resistant Gram-negative isolates were subjected to carbapenemase detection. Three phenotypic methods like Modified Hodge Test (MHT), RAPIDEC® CARBA NP kit (bioMérieux, France) and Chromogenic agar were used and a cartridge based molecular method Xpert® Carba-R (Cepheid) was used on all the study samples for detection of carbapenemases.

Results: The results of MHT, RAPIDEC® CARBA NP and CHROMagar were same for both Enterobacteriaceae and Non Fermenters (except for CHROMagar, which is applicable only for Enterobacteriaceae). Xpert® Carba R could not detect genes in all the phenotypically positive organisms for carbapenemase production. However, there was no statistically significant difference between the three phenotypic tests and Xpert® Carba R used for the detection of carbapenem resistance.

Conclusion: Preserving the last resort antimicrobials is the need of the hour, as there are few therapeutic options for treating infections caused by carbapenem-resistant bacteria. Early detection, followed by strict implementation of infection prevention and control strategies to stall the dissemination of such organisms is the best way and needs to be implemented on a war footing.