Molecular Detection of Carbapenemase Enzymes Directly from Positive Blood Cultures Using Xpert Carba-R

Abstract

Objective The performance of Xpert Carba-R assay for the direct identification of carbapenemases directly from positive blood culture vials was evaluated. Materials and Methods In total, 176 positively flagged blood culture vials, yielding carbapenem-resistant GNB (CR-GNB), were enrolled for the detection and differentiation of blaKPC, blaNDM, blaVIM, blaOXA-48, and blaIMP using Xpert Carba-R. Results Klebsiella pneumoniae (76/176, 43.1%), Acinetobacter baumannii complex (67/176, 38%), and Escherichia coli (29/176,16.4%) were the predominant isolates. Overall, NDM production was the commonest (61/176, 34.6%), followed by the co-production of NDM + OXA-48 and the absence of any CR gene (44/176, 25%), followed by OXA-48 (27/176, 15.3%). In CR K. pneumoniae, the co-production of NDM + OXA-48 was most frequent (34/76, 44.7%), whereas in the A. baumannii complex, no CR gene was detected in the majority of isolates (38/67, 56.7%). bla NDM was the commonest gene in E. coli (18/29, 62%) and A. baumannii complex (26/67, 38.8%). Conclusion Xpert Carba-R can identify the molecular mechanism of CR within hours after a blood culture turns positive and, thus, has the potential for optimization of antimicrobial therapy, choosing appropriate novel β-lactam combination agents, as well as infection control interventions.

Keywords

• blood culture
• carbapenemase
• xpert carba-r