Triple-disk assay for phenotypic detection of predominant Carbapenemases

Carbapenems form an integral part of treatment regimen for serious and multi drug resistant Gramnegative bacterial infections. However, there are reports on increasing prevalence of carbapenem resistance in clinical isolates of Enterobacteriaceae mainly due to the production of metallo-β-carbapenemases (MBL),1 Klebsiella pneumonia carbapenemase (KPC)2 and ampC β-lactamases (AmpC)3. Thus, there arises an urgent need for establishment of a sensitive phenotypic assay that can facilitate simultaneous detection of MBL, KPC and AmpC. Recent studies have reported the use of β-lactum inhibitors coupled with meropenem disks for simple and accurate identification of carbapenemase producing organisms; for example, 3-aminophenylboronic acid (APBA), dipicolinic acid (DPA), and simultaneous use of APBA and cloxacillin (CLX) for detection of KPC, MBL and AmpC with porin loss respectively4. Thus, the purpose of this study was to determine the most predominant carbapenemase using the triple-disk assay in carbapenem resistant clinical isolates of Enterobacteriaceae.