Rapid identification of Gram-negative pathogens from positive blood cultures using MALDI-TOF MS following short-term incubation on solid media.

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Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) enables the timely and reliable identification of microbes. The rapid identification of Gram-negative bacteria (GNB) in bloodstream infections is of critical importance. Several protocols have been proposed for the application of MALDI-TOF MS on samples from positive blood cultures (BCs) within the same day of BC positivity detection. The majority of these protocols include sample preparation steps with the use of chemicals or repeated centrifugations in order to avoid biases from human cells and proteins from the BC broth. These additional steps increase the hands-on processing time and the cost of identification. A different approach is to perform a MALDI-TOF MS analysis using biomass from briefly incubated subcultures on solid media. The present study discusses the findings of previous studies regarding the rapid identification of GNB from positive BC broth using MALDI-TOF MS following a short-term incubation period on solid media without any other additional steps or procedures.