Identification of emesis-causing Bacillus cereus strains by polymerase chain reaction: preliminary results

Bacillus cereus can give rise to two distinct forms of food borne disease, the diarrehoealand emetic syndromes. The second one is characterized by symptoms of nausea andvomiting which appear within 1–4 h from ingestion of the contaminated food. The emeticsyndrome is believed to be associated with an emetic toxin preformed in the food.Cooked rice and farinaceous foods such as pasta, noodles and cakes are consideredthe most common vehicles (Shinagawa et al., 1996). The emetic toxin is a cyclic dodecadepsipeptidenamed cereulide. It is resistant to pH changes and high temperature, resemblingthe staphylococcal enterotoxins and its activity is evident at low doses(Agata et al., 2002). For the detection of enterotoxic Bacillus cereus strains diagnosticmolecular assays such as PCR–based methods and immunological methods based on thedetection of the Hbl-L2 component (BCET-RPLA) have been performed. On the contrary,are not yet available commercial diagnostic kits for the detection of Bacillus cereusemetic strains (Guinebretiere et al., 2002). Three different methods for identificationof the emetic toxin have been described in recent years: the Hep-2 (larynx carcinoma)cells vacuolation assay, LC-MS analysis and a biological assay based on cereulideinducedinhibition of the motility in boar spermatozoa. According to Andersson et al.(2004), the cereulide producing Bacillus cereus strains are not able to hydrolyze starch.Recently, Ehling-Schulz and coworkers (2004) have identified a genomic DNA fragmentof 635 pb codifying for cereulide, and developed specific primers for the detection ofemetic Bacillus cereus strains.[...]