Purpose: VIDAS UP E. coli Serogroups (ESPT) was developed as a global method using phage recombinant proteins for the immuno-concentration (IC) of E. coli serogroups O157, O26, O103, O111, O145, O45 and O121 from food enrichments. IC will be used both for screening and confirmation steps. The aim of this study was to compare the new alternative method with the ISO 13136 standard.
Methods: For the alternative method, 375 g artificially contaminated raw beef products were ¼ diluted in a selective pre-warmed BPW and enriched for 10 h at 41.5 ± 1°C. For the reference method, 25 g samples were 1/10 diluted in BPW and enriched for 20 h at 37 ± 1°C. DNA was extracted using VIDAS ESP1 protocol or commercial lysis and analyzed by PCR (eae, stx, O-groups). Any positive samples were confirmed by immuno-concentrating the STEC strains with VIDAS ESP2 protocol or commercial IMS from the enrichment broth and streaking the immuno-concentrated samples onto selective agar plates. After incubation, typical colonies were further confirmed by SLIDEX E. coli tests and/or PCR tests.
Results: Among the 56 tested samples, 41 were obtained positive by both the methods. The results obtained for the two methods, in the tested experimental conditions described above, are comparable.
Significance: This study has demonstrated that the VIDAS ESPT assay is a promising tool to screen and isolate STEC strains from food enrichment. This complete alternative solution will provide technical and economic advantages to the food industry for routine testing.