Establishing a MALDI-TOF-TOF-MS method for rapid identification of three common Gram-positive bacteria (Bacillus cereus, Listeria monocytogenes, and Micrococcus luteus) associated with foodborne diseases

Abstract

We aimed to establish a method for the rapid identification of three common Gram-positive bacteria (Bacillus cereus, Listeria monocytogenes, and Micrococcus luteus) associated with foodborne diseases. MALDI-TOF-MS was used to determine the effects of sample pretreatment, culture medium, and culture time on the identification results. Then, MALDI-TOF-TOF-MS was used to establish an optimized method and further explore the effects of culture time on secondary proteins. Among the three sample pretreatment methods, formic acid extraction outperformed direct transfer and extended direct transfer, resulting in more protein peaks and higher peak intensity in B. cereus culture samples. However, with different culture times (1-7 d), ion peaks of all bacterial proteins were relatively stable according to MALDI-TOF-TOF-MS data. The protein peaks of B. cereus (1430 m/z), L. monocytogenes (2100 m/z), and M. luteus (2140 m/z) were split into small ion peaks at 1162, 1465, and 1625 m/z, respectively. After 7 d of culture, the secondary spectra, peak intensities, and peak values of formic acid-treated samples were relatively stable, indicating that secondary protein peaks were less affected by culture time. It provides a new approach for the routine identification and market supervision of food safety in China.

Evaluation of microbiome and physico-chemical profiles of fresh fruits of Musa paradisiaca, Citrus sinensis and Carica papaya at different ripening stages: Implication to quality and safety management

“…Similar to other authors [ 30 ], the spectra were produced by applying the Compass Satellite software, and the Microflex LT device was used for fast and accurate identification of bacterial colonies isolated from the fruit samples. A spectra score of 2.300–3.000 indicates that the identification of bacterial species has high reliability, 2.000–2.299 indicates the identification of possible species, 1.700–1.999 indicates the identification of possible genus, and 0.000–1.699 indicates that the identification result is unreliable.…”

Applications of MALDI-MS/MS-Based Proteomics in Biomedical Research

“…LC-ESI-MS/MS is the main technology in microbiological research, unlike MALDI, which occupies the clinical microbiology laboratory market despite its low possibility to target specific protein biomarkers or to handle complex microbial samples [ 136 ]. MALDI-ToF/ToF MS, complementary to MALDI-ToF MS and LC-ESI-MS/MS techniques, is useful for characterization of protein patterns, protein biomarkers, and whole proteomes for pathogenic bacteria [ 19 ] as well as for identification of bacteria based on secondary protein peaks, improving the identification of foodborne pathogens, such as Bacillus cereus , Listeria monocytogenes , and Micrococcus luteus [ 137 ]. Furthermore, MALDI-ToF/ToF coupled with MALDI-MSI can assure the discrimination between isomeric compound in ion images [ 138 ].…”

Synthesis, Identification and Antibacterial Activities of Amino Acid Schiff Base Cu(II) Complexes with Chlorinated Aromatic Moieties

“…These bacterial strains were chosen in order to have a good representativity of bacterial morphologies, cell grouping and cell wall structures, which are important factors influencing resistance to antibacterial molecules. Moreover, the species studied are described as human pathogens regarding E. coli [18] and S. saprophyticus [19], or in food poisoning with B. subtilis [20] and M. luteus [21]. The first group (Table 1, Cn.1, entries 1-8) was chosen for its various functions led by the amino acids (R 1 and R 2 ), as well as the presence of 2 or no chlorides (R 3 and R 5 ).…”