Application of metabolomics analysis to aid in understanding the pathogenicity of different lineages and different serotypes of Listeria monocytogenes.

Listeria monocytogenes is a foodborne pathogen with high mortality in young children, elderly persons, pregnant women, and immune-compromised individuals. Most human listeriosis cases are associated with four serotypes (1/2a, 1/2b, 1/2c and 4b) within lineages I and II. The intracellular metabolic changes in L. monocytogenes from different lineages and serotypes remain unclear. Here, a non-targeted metabolomics strategy, based on ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) coupled with chemometrics was performed to analyze the metabolic fluctuations in the lineages and serotypes of L. monocytogenes. In the aggregate, 93 L. monocytogenes isolates (two lineages and four serotypes) were investigated, and a total of 48 differential biomarker metabolites were identified. Twenty differential metabolites were observed at the lineage level, while the others were found at the serotype level. At the lineage level, significantly lower contents (fold change [FC] = 3.60) of γ-aminobutyric acid (GABA) was found in lineage II strains, as compared to lineage I strains. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enrichment analysis showed that different substances between lineages I and II participated in multiple metabolic pathways, among which pyrimidine metabolism, purine metabolism, and aminoacyl-tRNA biosynthesis were significantly enriched. The major significantly upregulated (P < 0.05) metabolites, including uridine 5'-monophosphate, uridine, guanosine monophosphate, and guanosine, in lineage II strains affect the synthesis of DNA and RNA. At the serotype level, the upregulation of urea precursor substances produced by the purine metabolism pathway in serotype 4b strains may be one reason for the increased virulence of serotype 4b strains, compared to other serotype strains. In addition, the upregulation of pyridoxine in the vitamin B6 pathway in 4b strains was also observed. The differential metabolic pathway of 1/2a and 1/2c strains is nucleotide metabolism, which could lead to differences in the biosynthesis of DNA and RNA of the strain and further affect the growth and proliferation of strains.