Bacterial identification by mass spectrometry

Abstract

Mass spectrometry has become an important tool for the clinical microbiologist for bacterial identification. Because matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) has been shown to provide reliable protein profiling data to identify many bacteria, three commercially available instruments are available. Phage amplification (PA) has added new dimensions including sensitivity, specificity, and reduced culturing time to bacterial characterization by MALDI-TOF-MS-based protein identification. In this procedure, a sample suspected of containing a target bacterium is infected with a species-specific phage and allowed to incubate for two to three hours. If an increase in phage protein is observed in the MALDI spectrum, amplification has occurred and is indicative of the presence of the target bacteria. As an extension of this, a rapid method of determining antibiotic resistance using PA with MALDI-MS has also been developed. Other non-protein-based mass spectrometry techniques for bacterial identification have also been explored. As an example, fatty acid profiling employing MALDI with CaO as a saponification catalyst has been shown to provide highly specific identification to the strain level. A comparison of metal oxide FA profiles to protein profiles obtained from a commercial instrument is presented.