Evaluation of the double-disk synergy test for New Delhi metallo-β-lactamase-1 and other metallo-β-lactamase producing gram-negative bacteria by using metal-ethylenediaminetetraacetic acid complexes

• Published in: Microbiology and immunology 2013-05, Vol.57 (5), p.346-352
• Main Authors: Fujisaki, Momoko, Sadamoto, Shinya, Hishinuma, Akira
• Format: Article
• Language: English
• Subjects: Bacteriological Techniques - methods; beta-Lactamase Inhibitors; beta-Lactamases - analysis; double-disk synergy test; Edetic Acid - metabolism; Enzyme Inhibitors - metabolism; gram-negative bacteria; Gram-Negative Bacteria - enzymology; metallo-β-lactamase; Sensitivity and Specificity; β-lactamases
• ISSN: 0385-5600; 1348-0421
• DOI: 10.1111/1348-0421.12042

New Delhi metallo‐β‐lactamase‐1 (NDM‐1), one of the metallo‐β‐lactamases (MBLs), has been identified from clinical isolates worldwide. Rapid detection of NDM‐1 producers is necessary to prevent their dissemination. Seven types of EDTA complexes were evaluated as MBL inhibitors in double‐disk synergy tests (DDSTs), resulting in detection of the first isolate of NDM‐1‐producing Escherichia coli (NDM‐1 Dok01) in Japan. NDM‐1 Dok01 was detected when EDTA magnesium disodium salt tetrahydrate (Mg‐EDTA), EDTA calcium disodium salt dihydrate, EDTA cobalt disodium salt tetrahydrate and EDTA copper disodium salt tetrahydrate were used as MBL inhibitors. The sensitivity and specificity of DDSTs using Mg‐EDTA for 75 MBL producers and 25 non‐MBL producers were 96.0% and 100%, respectively. These findings indicate that the DDST method using Mg‐EDTA can detect MBL‐producing strains, including NDM‐1 producers.