Behavior of an Emetic Bacillus cereus Strain in Rice Food (original) (raw)

Subject description: This article deals with the possible competitiveness of emetic B. cereus against nonemetics, likely to confer a development advantage to the first mentioned. The goal of this study was to evaluate the behavior of an emetic strain with respect to other B. cereus contaminants. Method: A rifampicin-resistant mutant of the emetic strain k5975c was grown in Luria-Bertani. Broth overnight at 30°C, then inoculated in cooked rice or in naturally contaminated rice and incubated for 24 h at 23°C and 30°C. The emetic toxin and its toxicity were detected using the boar sperm motility inhibition bioassay and the liquid chromatography-ion trap mass spectrometry (LC-MS). Results: With an inoculum level of ca. 6 log CFU g-1, the emetic strain showed unhampered growth in rice contaminated by other B. cereus at both incubation temperatures, although it did not inhibit the growth of B. cereus contaminants. When the inoculum level of the emetic strain was reduced to ca. 3 log CFU g...