Detection of bacteria from biological mixtures using immunomagnetic separation combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A rapid method for identifying specific bacteria from complex biological mi xtures using immunomagnetic separation coupled to matrix-assisted laser des orption/ionization time-of-flight mass spectrometry has been developed. The technique employs commercially available magnetic beads coated with polyco lonal antibodies raised against specific bacteria and whole cell analysis b y MALDI-MS. A suspension of a bacterial mixture is mixed with the immunomag netic beads specific for the target microorganism. After a short incubation period (20 mins) the bacteria captured by the beads are washed, resuspende d in deionized H2O and directly applied onto a MALDI probe. Liquid suspensi ons containing bacterial mixtures can be screened within Ih total analysis time. Positive tests result in the production of a fingerprint mass spectru m primarily consisting of protein biomarkers characteristic of the targeted microorganism. Using this procedure, Salmonella choleraesuis was isolated and detected from standard bacterial mixtures and spiked samples of river w ater, human urine, and chicken blood. Copyright (C) 2001 John Wiley & Sons, Ltd.