APPLICATION OF MALDI- TOF MS TECHNOLOGY TO THE IDENTIFICATION AND CHARACTERIZATION OF PATHOGENS IN DAIRY INDUSTRY

The prerequisite of any microbial identification technique, especially in food industry, is its accuracy. Furthermore, it should be easy to perform, fast and cost-effective to ensure safe products and identify their microbial contamination. In this study, we tested Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) as an efficient tool allowing identification of bacterial isolates with high confidence and speed. Five bacterial species were isolated from pasteurized milk samples collected from different steps of their line production, in a local dairy company in Constantine, Algeria. The isolates were analyzed by MALDI-TOF MS method and results were compared with those provided by sequencing of the 16S rDNA gene in order to confirm the identification. All bacterial isolates were successfully identified by MALDI-TOF MS method to the species level (scores ≥2). In parallel, 16S rDNA gene sequencing analysis identified the five isolates to the species level (≥99% sequence similarity). The results of MALDI-TOF MS-based identification of the bacterial isolates studied showed a total concordance (100% same species) for isolates designed S1, S2 and B2 to those of the reference method (16S rDNA gene sequencing), except for two cases (isolate B1 and B3), were the identification by both proteomic and genomic methods coincided at the genus level. This study suggests that comparatively to 16S rDNA gene sequencing which provides limited results; MALDI- TOF MS is a highly sensitive and rapid method that could be used to identify pathogens in dairy industry.