The Rapid Identification of Intact Microorganisms by Matrix‐assisted Laser Desorption/Ionization‐Time of Flight Mass Spectrometry

A variety of Gram-positive and Gram-negative intact bacterial cells have been analysed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOFMS). The bacterial cells provided fingerprint mass spectra with discrete peaks being observed over the mass range from 3 to 40 kDa. The spectra show both more peaks and peaks at a higher mass/charge ratio than have hitherto been reported for these microorganisms and would appear to provide a profile of cellular proteinaceous material. The spectra are shown to be reproducible over variable time periods of up to three months and factors affecting reproducibility are discussed. The procedure, which requires minimal sample preparation, yields results in 30–40 min and allows visual identification of species- and strain-specific biomarkers for the characterization of the organisms. The importance of accurately defining sample preparation methodologies is central to the ability of the technique to generate reliable and reproducible data.