Carbohydrate profiling of bacteria by gas chromatography–mass spectrometry and their trace detection in complex matrices by gas chromatography–tandem mass spectrometry

Abstract

Bacterial cellular polysaccharides are composed of a variety of sugar monomers. These sugars serve as chemical markers to identify specific species or genera or to determine their physiological status. Some of these markers can also be used for trace detection of bacteria or their constituents in complex clinical or environmental matrices. Analyses are performed, in our hands, employing hydrolysis followed by the alditol acetate derivatization procedure. Substantial improvements have been made to sample preparation including simplification and computer-controlled automation. For characterization of whole cell bacterial hydrolysates, sugars are analyzed by gas chromatography–mass spectrometry (GC–MS). Simple chromatograms are generated using selected ion monitoring (SIM). Using total ion GC–MS, sugars can be readily identified. In more complex clinical and environmental samples, markers for bacteria are present at sufficiently low concentrations that more advanced instrumentation, gas chromatography–tandem mass spectrometry (GC–MS–MS), is preferred for optimal analysis. Using multiple reaction monitoring, MS–MS is used (replacing more conventional SIM) to ignore extraneous chromatographic peaks. Triple quadrupole and ion trap GC–MS–MS instruments have both been used successfully. Absolute chemical identification of sugar markers at trace levels is achieved, using MS–MS, by the product spectrum.