Real-time PCR assay allows detection of the New Delhi metallo-β-lactamase (NDM-1)-encoding gene in France

In this study, we report the development of a rapid real-time polymerase chain reaction (PCR) assay with TaqMan probe to detect the New Delhi metallo-β-lactamase (NDM-1)-encoding gene directly from bacterial isolates. The specificity of the assay was verified in silico as well as with a large panel of 84 clinically relevant bacteria, including the Klebsiella pneumoniae NCTC 13443 NDM-1-positive reference strain. Using this assay retrospectively on a local series of 44 K. pneumoniae isolates from Marseille Hospitals (France), it was possible to detect and identify an NDM-1-producing K. pneumoniae strain isolated from bronchoalveolar lavage in April 2010 from a French patient repatriated from India after a motorbike accident. Standard PCR amplification and sequencing of the entire NDM-1 gene from this isolate was also performed and the amino acid sequence showed 100% homology with the NDM-1 protein from the K. pneumoniae reference strain. We believe that this real-time PCR assay would be a powerful tool that could be added to other molecular detection assays such as detection of KPC- or OXA-encoding genes for rapid screening and/or identification of carbapenem-resistant bacterial isolates from patients returning from the Asian continent that could be implemented in a point-of-care strategy.