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Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) for strain-typing of Campylobacter jejuni

Abstract

Background: Multilocus sequence typing (MLST) and flagellin gene typing are methods currently used for the typing of Campylobacter jejuni. However, these molecular methods are expensive and time consuming; their implementation in a routine laboratory is therefore difficult. This work was designed to explore matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) as a new typing system for Campylobacter directly from culture on agar plates. Methods: In this study, 20 randomly selected human Campylobacter jejuni isolates belonging to 8 sequence types (ST) and 4 clonal complexes (CC) were investigated on a VITEK MS RUO system (bioMérieux, Marcy l’Etoile, France). The presence or absence of distinct spectral peaks as potential strain-specific biomarkers for CC and ST was analysed. A formic acid extraction was performed and all isolates were smeared in quadruplicate. One μL of CHCA matrix solution was applied on each bacterial deposit and disposable MALDI targets were used. The studied masses ranged from 2.000 to 20.000 Da. Results: Considering the 80 different spectra obtained by the VITEK MS RUO system, 60 peaks were detected in all spectra. Several specific peaks were found for CC021, ST356, ST572 and ST021. Conclusion: This preliminary study suggests that a standard MALDI-TOF MS procedure is a promising tool for the typing of Campylobacter jejuni.

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