Detection of carbapenemase-producers: Evaluating the performance of the carbapenem inactivation method and Carba NP...

With a worrisome surge of carbapenem-resistant bacterial isolates, the diagnostic arsenal has become in dire need of affordable and timely assays to detect the rapidly transmissible carbapenemases. Employing multiplex PCR as a reference method, the purpose of the present study was to compare the performance of the carbapenem inactivation method (CIM) and the Carba NP test in the detection of carbapenemase-producers.

A panel of 203 Gram-negative bacterial isolates screened for carbapenem resistance were subjected to the CIM and Carba NP test. The results were compared with multiplex PCR targeting various carbapenemase genes.

According to multiplex PCR, 92 (45.3%) of 203 isolates were found to harbour one or more carbapenemase genes, with bla_NDM and bla_KPC being the most commonly encountered. The sensitivity and specificity of the CIM were 95.7% and 95.5% respectively, whilst those of the Carba NP test were 75.0% and 99.1%, respectively. Both methods were found to be rapid and reliable in the detection of carbapenemases and showed a high agreement with multiplex PCR.

As the list of carbapenemase genes continues to expand, the reliability of PCR has become doubtful; hence, the CIM and Carba NP test could offer promising alternatives, with the CIM being of a lower cost and less labour intensive.