Application of MALDI-TOF MS for the Identification of Food Borne Bacteria

Abstract

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has recently emerged as a powerful tool for the routine identification of clinical isolates. MALDI-TOF MS based identification of bacteria has been shown to be more rapid, accurate and cost-efficient than conventional phenotypic techniques or molecular methods. Rapid and reliable identification of food-associated bacteria is also of crucial importance for food processing and product quality. This review is concerned with the applicability of MALDI-TOF MS for routine identification of foodborne bacteria taking the specific requirements of food microbiological laboratories and the food industry into account. The current state of knowledge including recent findings and new approaches are discussed.

Keywords: MALDI-TOF MS; bacteria; food isolates; food microbiology; species identification.

Fig. (1)

Principle of the MALDI method. The analyte-matrix crystals are irradiated with a pulsed laser. This leads to the desorption of the analyte molecules and protons are transferred from the matrix to the analyte (modified according to [10]).

Fig. (2)

MALDI analyses with a time of flight mass analyzer (modified according to [10]).

Fig. (3)

Protein fingerprint of an Escherichia coli isolate. The assignment of the main peaks to the m/z ratios of the ribosomal proteins of E. coli indicates that ribosomal proteins are principal components in the MALDI-TOF MS based identification of bacteria (modified according to [12]).

Fig. (4)

Identification of bacteria on the basis of mass spectrometric protein fingerprints. Microorganisms are pre-treated as described or directly applied onto a target plate and overlaid with matrix. The target is introduced into the mass spectrometer to record the fingerprints in the range of about 2 000-20 000 m/z. A typical mass spectrum is shown. Data are analysed automatically.