Matrix-assisted laser desorption ionization-time of flight mass spectrometry 
(MALDI-TOF MS) is a potentially useful tool for the detection of antimicrobial 
resistance, especially that conferred by β-lactamases. Here we describe a 
modification of a previously reported MALDI-TOF MS meropenem hydrolysis assay. 
The modified method was validated on 108 carbapenemase-producing members of the 
Enterobacteriaceae, two NDM-1-producing Acinetobacter baumannii isolates, and 35 
carbapenem-resistant enterobacteria producing no carbapenemase. The detection of 
carbapenemases by MALDI-TOF MS seems to be a powerful, quick, and cost-effective 
method for microbiological laboratories.