Serotype-identifying ions in Listeria monocytogenes using matrix-associated laser desorption ionization-time of flight mass spectrometry.

is a foodborne pathogen that can cause a potentially life-threatening infection, and almost all cases of human listeriosis are caused by isolates in serotypes 1/2a, 1/2b, 1/2c, and 4b. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a rapid, accurate, and high-throughput tool for clinical diagnosis and microbiological research. In the current study, we examined the potential of MALDI-TOF MS for rapid identification of the foodborne pathogen and to identify high-risk serotypes. To achieve this, MALDI-TOF MS was applied to 50 strains. All strains were identified as species based on pattern matching against reference spectra for the species. Importantly, 83 specific mass ions were consistently and uniquely found in high-risk serotypes 1/2a, 1/2b, 1/2c, and 4b. These 83 mass ions were also unique to specific combinations of these serotypes, which enabled specific identification of these four serotypes using MALDI Biotyper analysis. Hence, this method shows potential for using MALDI-TOF MS for the rapid identification of species and to discriminate high-risk serotypes through specific serotype-specific biomarker ions.