In vitro cost-effective methods to detect carbapenemases in Enterobacteriaceae

The rise in carbapenemases-producing organisms has challenged the scientific community. Infections caused by these bacteria have limited treatment options. There are various types such as Klebsiella pneumoniae carbapenemase (Ambler class A), metallo-beta-lactamases of VIM-type, IMP-type, NDM-type (Ambler class B), and OXA-48-types (Ambler class D). An efficient strategy for detection of carbapenemase producers is important to determine the appropriate therapeutic modalities. In this study, four methods - Carba NP test, modified Carba NP (MCNP) test, carbapenem inactivation method (CIM) test, and Rapidec Carba NP kit test were evaluated. We evaluated an in-house MCNP test to detect carbapenemase production using a single protocol which gave reliable results. Furthermore, CIM using routine antibiotic discs gives good results. Both these tests were found to be cost-effective.