Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry assay was able to detect carbapenemase producers, including SIM-1 or OXA-51, within 4 hours using 20 mu L of 0.5 g/L ertapenem solution as a substrate. This assay is more rapid and accurate than the modified Hodge test and 3-dimensional extract bioassay. Hence, it can be used an alternative test to identify carbapenemase-mediated carbapenem resistance in Gram-negative bacteria. (C) 2013 Elsevier Inc. All rights reserved.