Cereulide is an emetic toxin produced by some strains of Bacillus cereus. This bacterial toxin, a cyclic 1.2 kDa dodecadepsipeptide, is stable to heat and acids and causes nausea and vomiting when ingested via contaminated food. This work aimed to develop and validate a targeted analytical method applying liquid chromatography-tandem mass spectrometry (LC–MS/MS) to quantify this toxin in food and human faeces. Samples were extracted with acetonitrile in the presence of ¹³C₆-cereulide, a labelled internal standard, and purified by centrifugation and filtration. The limits of quantification were 0.5 and 0.3 µg kg⁻¹ for food and faeces, respectively. The linearity of the method was very good, with calculated R² values above 0.995. The mean recovery of the method was within the acceptable range of 70.0%–120.0%, the repeatability was not higher than 7.3%, and the highest intra-laboratory reproducibility was 8.9%. The estimated range for the expanded measurement uncertainty was between 5.1% and 18.0%. The LC–MS/MS method was used to analyse one food sample (rice) from a Belgian foodborne outbreak and five faecal samples from patients with clinical symptoms after consumption of the contaminated rice. The levels of cereulide were 12.22 µg g⁻¹ for food and between 6.32 and 773.37 ng g⁻¹ for faecal samples.

Modeling human genetic diseases and cancer in lab animals has been greatly aided by the emergence of genetic engineering tools such as TALENs and CRISPR/Cas9. We have previously demonstrated the ease with which genetically engineered Xenopus models (GEXM) can be generated via injection of early embryos with Cas9 recombinant protein loaded with sgRNAs targeting single or multiple tumor suppressor genes. What has been lacking so far is the possibility to propagate and characterize the induced cancers via transplantation. Here, we describe the generation of a rag2 knockout line in Xenopus tropicalis that is deficient in functional T and B cells. This line was validated by means of allografting experiments with primary tp53^−/− and apc^+/−/tp53^−/− donor tumors. In addition, we optimized available protocols for the sub-lethal irradiation of wild-type X. tropicalis froglets. Irradiated animals also allowed the stable, albeit transient, engraftment of transplanted X. tropicalis tumor cells. The novel rag2^−/− line and the irradiated wild-type froglets will further expand the experimental toolbox in the diploid amphibian X. tropicalis and help to establish it as a versatile and relevant model for exploring human cancer.