Improved MALDI‐MS method for the highly sensitive and reproducible detection of biomarker peaks for the proteotyping of Salmonella serotypes


Fukuyama Y, Ojima-Kato T, Nagai S, Shima K, Funatsu S, Yamada Y, Tamura H, Nomura S, Ogata K, Sekiya S, Iwamoto S, Tanaka K


The rapid identification and classification of pathogenic microorganisms, including Salmonella enterica, is important for the surveillance and prevention of foodborne diseases. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been shown to be an effective tool for the rapid identification of microorganisms. In a previous report, a mass database consisting of twelve biomarker proteins, S8, L15, L17, L21, L25, S7, superoxide dismutase (SodA), peptidylprolyl cis-trans isomerase C, Gns, YibT, YaiA and YciF, was introduced for the serotyping of Salmonella enterica via MALDI-MS (Applied Microbiology and Biotechnology, 2017, 101, 8557-8569). However, the reproducibility of peak detection of biomarkers such as SodA at m/z 23,000 was poor. We report here an optimized MALDI-MS method for detecting these biomarkers with high sensitivity and reproducibility. The issue was solved by controlling the bacterial concentration at 1×10~1×102 MFU (3×106 ~3×107 CFU/μL, as calculated from the MFU), using the colony suspension supernatant obtained by centrifugation, and using matrix additives such as methylenediphosphonic acid and N-decyl-β-D-maltopyranoside. We propose that the method including the above steps is one of the best for detecting biomarkers with high sensitivity and reproducibility.

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