Abstract
Due to its food-poisoning potential, Bacillus cereus has attracted the attention of the food industry. The cereulide-toxin-producing subgroup is of particular concern, as cereulide toxin is implicated in broadscale food-borne outbreaks and occasionally causes fatalities. The health risks associated with long-term cereulide exposure at low doses remain largely unexplored. Natural substances, such as plant-based secondary metabolites, are widely known for their effective antibacterial potential, which makes them promising as ingredients in food and also as a surrogate for antibiotics. In this work, we tested a range of structurally related phytochemicals, including benzene derivatives, monoterpenes, hydroxycinnamic acid derivatives and vitamins, for their inhibitory effects on the growth of B. cereus and the production of cereulide toxin. For this purpose, we developed a high-throughput, small-scale method which allowed us to analyze B. cereus survival and cereulide production simultaneously in one workflow by coupling an AlamarBlue-based viability assay with ultraperformance liquid chromatography–mass spectrometry (UPLC-MS/MS). This combinatory method allowed us to identify not only phytochemicals with high antibacterial potential, but also ones specifically eradicating cereulide biosynthesis already at very low concentrations, such as gingerol and curcumin.
Highlights
B. cereus is responsible for an increasing number of food-borne diseases resulting from food-borne infections and intoxications [1,2,3]
The 1.2 kDa peptide toxin cereulide [D-O-Leu D-Ala L-O-Val D-Val]3 is synthesized by a non-ribosomal peptide synthetase (NRPS) encoded by the ces operon located on the mega-plasmid pCER270, which shares its backbone with the anthrax toxin encoding pX01 plasmid of Bacillus anthracis [10,11,12]
We developed a high-throughput, small-scale method, which combines the detection of B. cereus viability and cereulide production by coupling an AlamarBlue-based viability assay with ultraperformance liquid chromatography–mass spectrometry (UPLC-MS/MS), using a microtiter plate format to assess the inhibitory potentials of commonly used food additives, extracts derived from industrial product admixtures, as well as select secondary compounds from plants with reported antibacterial activity
Summary
B. cereus is responsible for an increasing number of food-borne diseases resulting from food-borne infections and intoxications [1,2,3]. Food-borne infections often lead to gastrointestinal symptoms, evoked by various enterotoxins produced by re-germinated bacteria in the small intestine, while intoxications are caused by the emetic toxin cereulide preformed in foods [4,5]. Due to its small size of 1.2 kDa and chemical properties, cereulide (by contrast to bacterial cells or spores) cannot be removed by filtration or inactivated by heating or cooking during food production and processing. Once preformed in food contaminated with emetic B. cereus, cereulide cannot be eliminated prior to consumption. The prevention of toxin formation in food production and processing, as well as during food storage, is of utmost importance
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