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

Abstract

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 12 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 S. 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 to 1 × 102 MFU (3 × 106 to 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.

Proteotyping of Campylobacter jejuni by MALDI-TOF MS and Strain Solution Version 2 Software

“…As for the three strains doubly hitting the correct and the other groups with the same score of 7, adding a new biomarker to the database could help with accurate identification. However, at present, since we have not found any biomarkers other than Table 3 that can be detected stably, the sample preparation method may need to be improved, as examined for Salmonella enterica [ 34 ].…”

Performance of MALDI-TOF Mass Spectrometry (VITEK MS) in the Identification of Salmonella Species

“…Recently, MALDI-TOF MS has been commonly used as a routine identification method [ 5 , 6 ]. However, there are a few previous reports on the performance of VITEK MS in identifying Salmonella [ 11 , 12 , 13 ]. Guo et al [ 17 ] using 1025 bacteria isolated from clinical specimens, reported that VITEK MS exhibited good performance; however, only two strains of Salmonella were included in the report.…”

“…The performance of VITEK MS in identifying bacteria, fungi, and mycobacteria has been steadily evaluated [ 6 , 7 , 8 , 9 , 10 ]. However, only a few studies have evaluated the performance of VITEK MS in identifying Salmonella strains and serotypes [ 11 , 12 , 13 ]. This study aimed to evaluate the usefulness of MALDI-TOF VITEK MS for Salmonella identification using more than 1000 Salmonella strains, including 60 serotypes, isolated from human specimens.…”

Proteomics approaches: A review regarding an importance of proteome analyses in understanding the pathogens and diseases

“…The improved mass spectrometry approach for the absolute detection of biomarkers from Salmonella serotypes was introduced by Fukuyama and colleagues ( 116 ). In a cohort research, quantitative proteomics was used to uncover distinct biomarkers in the plasma of individuals with active tuberculosis.…”