The novel in vitro sperm micro assay distinguishes mitochondrial toxin producing Bacillus cereus from other B. cereus. It is based on the easily recorded response, motility inhibition, exhibited by boar spermatozoa exposed to mitochondrial toxins. Cereulide, the emetic toxin of B. cereus, is a mitochondrial toxin and is detected by this assay. The assay is nonlaborious, robust, not sensitive to age or storage of the culture plates and can be executed with equipment present in most laboratories. The assay can be executed in 15 min with a loop of biomass from culture plate. The full details and validation are described in Andersson et al 2004.
The test distinguishes mitochondrial toxins from other toxins when supplemented with functional staining (JC-1, calcein AM, PI). Full details are described in Hoornstra et al 2003.The presence of cereulide in the bacterial extract can be confirmed by chemical analysis. Bacterial extracts are analysed by liquid chromatography-ion trap mass spectrometry (LC-ion trap MS) using the mass ions m/z 1175 (Na+ adduct), m/z 1192, (K+ adduct), m/z 1154 (H+ adduct) and m/z 1171 (NH4+ adduct). The detection limit was 10 pg of cereulide per injection.