[Cereulide forming presumptive Bacillus cereus strains from food--differentiating analyses using cultural methods, LC-MS/MS, PCR, and infrared spectroscopy in consideration of thermotolerant isolates].

Pathogenic Bacillus cereus (B. cereus) cause two types of foodborne diseases: the diarrhoeal type and, after production of a heat stable toxin called cereulide, an emetic type. The identification of B. cereus in official food monitoring has been traditionally performed using the cultural procedure as described in method 00.00-25 according to section 64 of the German Food and Feed Law (LFGB). Strains isolated by this method are called "presumptive B. cereus" a collective name for B. cereus sensu strictu, B. thuringiensis and closely related Bacilli. Some potentially pathogenic thermotolerant isolates ("B. cytotoxicus") are not covered by this method. In this work Fourier-Transform-infrared spectroscopy (FT-IR) in combination with artificial neural network based data analysis was tested and verified for the further differentiation of "presumptive B. cereus" isolates and closely related Bacilli. For this purpose 122 Bacillus strains were, in addition to the section 64 LFGB method, assayed for formation of parasporal crystals, thermotolerant growth, PCR and LC-MS/MS. Based on this data a further FT-IR-method was developed for the differentiation of emetic B. cereus. Exemplarily, these methods were applied in a B. cereus related foodborne outbreak. In addition, the obtained FT-IR-spectra visualize the chain of infection.