Background: Rapid detection of carbapenemase-producing gram-negative bacilli (GNB) is required for optimal treatment of infected patients. We developed and assessed a new disk carbapenemase test (DCT). Methods: Paper disks containing 0.3 mg of imipenem and bromothymol blue indicator were developed, and the performance of the DCT were evaluated by using 742 strains of GNB with or without carbapenemases. Results: The paper disks were simple to prepare, and the dried disks were stable at -20° C and at 4° C. The DCT detected 212 of 215 strains (98.6% sensitivity with 95% confidence interval [CI] 96.0-99.5%) of GNB with known class A (KPC and Sme) and class B (NDM, IMP, VIM, and SIM) carbapenemases within 60 min, but failed to detect GES-5 carbapenemase. The DCT also detected all two Escherichia coli isolates with OXA-48, but failed to detect GNB with OXA-232, and other OXA carbapenemases. The DCT showed 100% specificity (95% CI, 99.2-100%) in the test of 448 imipenem-nonsusceptible, but carbapenemase genes not tested, clinical isolates of GNB. Conclusions: The DCT is simple and can be easily performed, even in small laboratories, for the rapid detection of GNB with KPC, NDM and the majority of IMP, VIM, and SIM carbapenemases.
Bibliographical noteFunding Information:
We thank Myung Sook Kim in the Section of Clinical Microbiology, Department of Laboratory Medicine, Yonsei University College of Medicine and Young Hee Seo in the Research Institute of Bacterial Resistance, Yonsei University College of Medicine for their invaluable help with this study.
© The Korean Society for Laboratory Medicine.
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