Combined disc methods for the detection of KPC- and/or VIM-positive Klebsiella pneumoniae: improving reliability for the double carbapenemase producers

Klebsiella pneumoniae strains co-producing klebsiella pneumoniae carbapenemase (KPC) and verona integron-encoded metallo-beta-lactamase (VIM) are frequently isolated in Greece and have also occurred in other European countries. Conventional combined disc tests exhibit low sensitivity against these emerging pathogens. We have evaluated modifications of the KPC/Metallo-β-Lactamase Confirmation kit (ROSCO) exhibiting high diagnostic value against KPC, VIM and KPC + VIM producers. The key changes were the inclusion of additional combined tablets containing meropenem plus two inhibitors (dipicolinic acid (1000 μg per tablet) for metallo-β-lactamases and a boronic acid derivative for KPCs) and the replacement of aminophenylboronic acid by phenylboronic acid (400 μg per tablet).