Establishment of three libraries of reference MALDI-ToF spectra for Salmonella, Yersinia and Campylobacter strains included in the CARE collection

Abstract summaryAim: MALDI-TOF Mass spectrometry is now commonly used for bacterial identification. In order to build a database to increase the number of reference spectra already existing in the Bruker commercial database, and to pave the way for further studies, three partners are working on producing reference spectra for Salmonella, Yersinia and Campylobacter, important public health pathogens included in the CARE collection.Methods: All strains were cultivated on non-selective nutrient agar at 30°C or 37°C for 18 H or 24 H (depending on the species). The protein extraction proposed by Bruker was performed in each case. A MALDI-TOF Bruker equipment was used to establish the libraries of reference spectra. Until now, the study focused on 22 strains of Yersinia, 58 strains of Salmonella. All raw spectra were analysed according to the established MSP protocol of the MALDI Biotyper® to remove suboptimal spectra (at least eight replicates, and each spot analysed three to four times). Acquired spectra were analysed with Bruker MBT explorer software and compared with spectra from the commercialized Bruker Daltonic Data Base covering 3239 species/entries (9607 MSP).Results: Highly reliable identification scores were obtained for Yersinia and Salmonella strains allowing the species identification.Conclusions: This work will contribute to the fine characterization of the reference material of the CARE collection implemented in the frame of the One Health European Joint Programme (OHEJP). The accumulation of standardized spectra for each bacteria of interest is essential to generate data for further studies such as the identification of biomarkers. Future work will include obtaining reference spectra for five species of Campylobacter