Evaluation of MASTDISCS combi Carba plus for the identification of metallo-β-lactamases, KPC and OXA-48 carbapenemase genes in Enterobacteriaceae clinical isolates.

The increasing frequency of class A KPC enzymes, class B metallo-β-lactamases (MBLs) and class D OXA-48 enzymes in Enterobacteriaceae makes their early identification urgent. A simple commercial MASTDISCS combi Carba plus disc system (MAST-Carba plus) was designed for the identification of MBLs, KPC and OXA-48 carbapenemase genes in Enterobacteriaceae. To validate the MAST-Carba plus, a total of 77 isolates of carbapenemase-producing Enterobacteriaceae (CPE) and 84 isolates of noncarbapenemase-producing Enterobacteriaceae (non-CPE) were selected for differentiation of the genes of Enterobacteriaceae by MAST-Carba plus. Meanwhile, the carbapenemase genes such as blaKPC , blaIMP , blaVIM , blaNDM-1 and blaOXA-48 were detected by PCR (polymerase chain reaction). Thus, when considered on the basis of PCR results, the sensitivity of MAST-Carba plus detection of KPC strains is 82·3%, the specificity is 100·0%, the positive predictive value is 100·0% and the negative predictive value is 92·4%. For MBLs strains, the sensitivity is 100·0%, the specificity is 97·1%, the positive predictive value is 84·6% and the negative predictive value is 100·0%. For OXA-48 strains, the sensitivity is 100·0%, the specificity is 99·4%, the positive predictive value is 80·0% and the negative predictive value is 100·0%. Our findings suggest that MAST-Carba plus is a rapid and promising method for identifying the MBLs, KPC and OXA-48 carbapenemase genes in Enterobacteriaceae, which could be exploited in basic microbiology laboratory to prevent the transmission of CPE. SIGNIFICANCE AND IMPACT OF THE STUDY: Not only detection of carbapenemases but also identification of their genes accurately and rapidly in Enterobacteriaceae is still a major challenge for clinical laboratories in order to prevent the transmission of carbapenemase-producing Enterobacteriaceae (CPE). Therefore, this study aimed to evaluate the performance of a new rapid method (MASTDISCS combi Carba plus) for the identification of metallo-β-lactamases (MBLs), KPC and OXA-48 carbapenemase genes in Enterobacteriaceae clinical isolates.