Abstract: Objective: To establish a matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) method to detect Campylobacter jejuni and Listeria monocytogenes in environmental samples from a chicken farm and samples from commercial live chickens using VITEK MS. Methods: The suspicious colonies of both bacteria were separated from the samples, and then suspended in matrix solutions consisting of mixtures of different proportions of ethanol, acetonitrile and water before identification by MALDI-TOF-MS. The effect of matrix solution composition on the bacterial detection was evaluated by examining the differences in characteristic peak value and relative abundance. Results: Significantly different matrix solutions were needed for the detection of Campylobacter jejuni and Listeria monocytogenes; the former did not require cracking by formic acid and was sensitive to trifluoroacetic acid (TFA), but the latter were just the opposite. A 30% water content in matrix solution (V/V) could avoid the lack of characteristic peak and enhance the detection rate. Conclusion: Control of the water content in matrix solution, TFA concentration and matrix concentration can enhance the number and relative abundance of characteristic peaks, and detection rate. The optimized matrix solution enables the rapid identification of foodborne pathogens, which was able to improve the timeliness of disease prevention and food-borne risk monitoring.

Key words: VITEK MS microbe identification system, Campylobacter jejuni, Listeria monocytogenes, matrix solution composition, mass spectrometric detection of microbes