Detection of Listeria in milk using non-targeted metabolic profiling of Listeria monocytogenes: A proof-of-concept application

Listeria is represented by ten known species, comprising pathogenic and non-pathogenic variants. Listeria monocytogenes is the type species and is primarily pathogenic to humans and causes serious illness. As a result, most countries have a zero tolerance towards the presence of Listeria in foods. Therefore, in order to ensure food safety, robust techniques for detection are required. This paper describes a proof-of-concept application of a metabolomic technique for the rapid detection of Listeria, applied to nutrient media and a complex food sample (milk) inoculated with a pathogenic Listeria strain (L. monocytogenes). It was found that a profile of intracellular and extracellular metabolites associated with L. monocytogenes could be obtained using gas chromatography, coupled to orthogonal acceleration time-of-flight mass spectrometry (GC-oaToFMS). Chemometric analysis showed that it is possible to differentiate between the uninoculated samples and samples inoculated with Listeria based on L monocytogenes metabolic activity. This research demonstrates that metabolomics has the potential for rapidly identifying food contaminated with Listeria and could provide a means for enhancing monitoring programmes and ensuring food safety.