Résumé original
Original abstract
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The validation of an impedance method was carried out against the European MPN reference method according to EN ISO 16140, with the view to providing an alternative to the reference test for rapid enumeration of Escherichia coli in live bivalve molluscs. Oysters (Crassostrea gigas), mussels (Mytilus edulis and Mytilus galloprovincialis) and burrowing bivalves (cockles Cerastoderma edule, clams Ruditapes decussatus and Ruditapes philippinarum, and tellins Donax trunculus) were tested during the validation study. The impedance method was first characterised with regard to linearity and relative accuracy (there was no deviation from linearity, and E. coli results was equivalent to those of the reference method), detection and quantification limits (67 and 130 E. coli per 100 g, respectively), and selectivity (typical E. coli signal, no significant interference of non-E. coli species). An inter-laboratory study was next performed to assess the relative accuracy of the impedance method as compared to the reference method (bias was non-significant or acceptable, from -0.18 to 0.29 log10 unit) and determine repeatability (0.38 to 0.85 log10 unit) and reproducibility (0.48 to 1.27 log10 unit,) that was shown to be similar to those of the reference method. The overall results demonstrate that the impedance method can be used as an alternative to the reference test for rapid enumeration of E. coli in live bivalve molluscs.
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