Diagnostic Efficacy of Carba NP Strip Test for Carbapenemase Detection

Abstract

Clinical isolates of carbapenem resistant Enterobacteriaceae (CRE) by carbapenemase production have now spread worldwide. Carbapenemase producers notoriously exhibit multidrug resistance phenotypes, making treatment of infections extremely difficult as they are able to hydrolyze a broad spectrum of β-lactams including the penicillins, cephalosporins, carbapenems and monobactam. They have the potential to spread rapidly in hospital environment and cause nosocomial infections with high mortality rates. Rapid identification of carbapenemase producing organisms is extremely important for timely detection, treatment and implementation of infection control measures to prevent their spread. Many phenotypic and molecular commercially available and in-house laboratory tests have been described for detection of carbapenemase. The Carba NP test is a phenotypic test for carbapenemase detection. It is based on hydrolysis of the β-lactam ring of imipenem by carbapenemases, leading to acid production that can be detected by the change of phenol red from red to yellow or orange. The Carba NP strip test is a recent modification of the Carba NP test by using filter paper as an inoculation medium for reading the color change and for decreasing the time of identifying the carbapenemase producing Enterobacteriaceae and Pseudomonas spp.