Detection of cesA mRNA from Bacillus cereus by RNA-specific amplification

Cereulide is the cyclic dodecadepsipeptide responsible for the emetic-type food-borne disease caused by Bacillus cereus. It is synthesized enzymatically by non-ribosomal peptide synthetases. In this study, we established an RNA-specific amplification assay for the detection of mRNA transcribed from the cesA gene, one of the 7 genes constituting the cereulide synthetase (ces) gene cluster of emetic-type B. cereus. The assay detected as few as 1000 copies of this RNA. Examination of the total RNAs extracted from 7 strains of cereulide-producing B. cereus, 6 strains of cereulide non-producing B. cereus, 6 strains of other Bacillus species, and 10 non-Bacillus strains showed that the assay specifically detected emetic-type B. cereus strains. RNA-specific amplification using RNA extracts provided comparable results to RT-PCR assays using RNA extracts and PCR assays using DNA extracts. The RNA-specific amplification assay is suitable for the detection of mRNA transcribed from the cesA gene.