COULD MALDI-TOF REPRESENT AN ALTERNATIVE TO SALMONELLA CONVENTIONAL SEROTYPING?

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Py, Jean-Sébastien | Cherchame, Emeline | Wilhelm, Amandine | Kerouanton, Annaëlle | Bonifait, Laetitia | Perrin-Guyomard, Agnes | Gassilloud, Benoît | Six, Sabrina Cadel

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International audience. Laboratories implied in surveillance need a rapid and not-expensive method for the most frequently isolated Salmonella serotypes. MALDI-TOF/MS could represent an alternative, however even if its ability to discriminate pathogens at genus and specie level was well established, at serotype level it remains scare. The aim of this study was to evaluate the potential of MALDI-TOF for typing the 12 serotypes considered to be of public health significance.Two-houndred-seventy-two Salmonella strains were phylogenetically characterized and their accessory genome explored with ResFinder, BactMet and vfdb databases1, 2, 3. Between two to ten strains, for each of the 12 major serotypes were selected based on their genomic diversity to create a reference spectrum and analyzed with a Microflex-LT after a full proteomic extraction. Eight deposits were run four independent times to acquire 32 spectra for each strain. The reference spectra were produced for each serotype after have grown each strain on two different culture media (Drigalski and TSYE) in three separate series. The repeatibility and reproducibilty were evaluated using different approaches: score analysis, Gelview spectra alignment and ClinProTools methods.Comparision of the results obtained using different approaches allowed us to underline that evaluation of the reproducibility was critical step which should be explored prior creation of a serotype database. Among the 12 Salmonella serotypes analyzed, Napoli, Enteridis, Heidelberg and Typhimurium were identifies with any statistical approache. Our results suggests that to create a reference spectra database at serotype level, an integrative approache with both genomic different strains and different culture media must be used.Funding acknowledgement: This study was supported by funding of the French Agency for Food, Environmental and Occupational Health & Safety (Anses) (France).References or website-links 1.https://github.com/afelten-Anses/ 2.ResFinder : Zankari, E.; Hasman, H.; Cosentino, S.; Vestergaard, M.; Rasmussen, S.; Lund, O.; Aarestrup, F. M.; Larsen, M. V., Identification of acquired antimicrobial resistance genes. J Antimicrob Chemother 2012, 67 (11), 2640-4.3.Chen, L.; Zheng, D.; Liu, B.; Yang, J.; Jin, Q., VFDB 2016: hierarchical and refined dataset for big data analysis--10 years on. Nucleic Acids Res 2016, 44 (D1), D694-7.

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