RAPID IDENTIFICATION OF INTACT WHOLE BACTERIA BASED ON SPECTRAL PATTERNS USING MATRIX-ASSISTED LASER DESORPTION IONIZATION WITH TIME-OF-FLIGHT MASS-SPECTROMETRY/

Matrix assisted laser desorption/ionization time-of-flight mass spectr ometry (MALDI-TOFMS) was investigated as a method for the rapid identi fication of whole bacteria, either by comparison with archived referen ce spectra or by co-analysis with cultures of known bacteria. Bacteria were sampled from colonies on an agar plate, mixed with the matrix, a ir-dried, and introduced in batches into the mass spectrometer for ana lysis. In the first experiment, both bacterial strains that had been p reviously analyzed to obtain reference spectra and other strains that had not been analyzed were blind-numbered and their spectra were obtai ned. Those strains that matched reference spectra were found to be cor rectly identified. A second experiment involved co-analysis of referen ce strains and bind-numbered strains under identical conditions; speci es-specific identification was demonstrated by comparison of spectra o f the blind-numbered strains with those of the standards. In all of th e spectra obtained in these experiments, each bacterial strain showed a few characteristic high-mass ions which are thought to be derived fr om bacterial proteins. This work represents the first reported instanc e of successful bacterial chemotaxonomy by MALDI-TOFMS analysis of who le cells. For the strains tested, the method is rapid and simple.