Performance characteristics of the Duopath® Cereus Enterotoxins assay for rapid detection of enterotoxinogenic Bacillus cereus strains

The Duopath® Cereus Enterotoxins test (Merck KGaA) is a newly developed gold-labeled lateral flow immunoassay for the detection of Bacillus cereus enterotoxins. The test uses monoclonal antibodies (MAbs) against the L2 component of hemolysin BL (Hbl) and NheB of the non-hemolytic enterotoxin (Nhe), respectively. The inclusivity and exclusivity of the assay was tested using 44 B. cereus, B. cereus group and Bacillus spp. strains. Apart from the B. mycoides type strain the results were in full agreement with those obtained by other immunological and molecular biological methods. The detection limit of the assay was 6 ng/ml for NheB and 20 ng/ml for the Hbl-L2-component, respectively. Using artificially and naturally contaminated food samples (n = 76) the assay was positive after 18–24 h enrichment if at least 102 enterotoxin producing B. cereus/g were present. After 30 h enrichment samples contaminated with as low as 1 enterotoxin producing B. cereus/g gave positive results. In addition, testing of suspected colonies for enterotoxin production is possible. The assay is easy to perform and results can be clearly read without instrumentation.