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

The increasing frequency of class A KPC enzymes, class B metallo-beta-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 bla(KPC), bla(IMP), bla(VIM), bla(NDM-1) and bla(OXA-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.