Fingerprint matching of E. coli strains with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of whole cells using a modified correlation approach.

We have developed a mathematical algorithm to compare and distinguish matrix-assisted laser desorption/ionization (MALDI) mass spectra of whole bacteria cells. This fingerprint matching technique eliminates the subjectivity involved in visually comparing two spectra to determine whether they match and it provides a quantitative measure of spectral similarity. Using it, we have distinguished twenty five different strains of a single bacteria species, E. coli. Cells are grown in culture, samples are prepared, and MALDI-TOF mass spectra are recorded for each strain. Pairs of spectra are compared by a modified cross-correlation procedure. This modified approach increases the sensitivity of correlation analysis to small spectral differences. The technique can be fine-tuned by varying the number of intervals into which spectra are divided.