The complete CoSYPS Path Food workflow was validated for the enrichment, detection, isolation and confirmation of the presence of
Listeria spp. and Salmonella spp. in beef carcass swab samples. The samples were analysed in parallel by the reference ISO methods and the
complete CoSYPS Path Food workflow as depicted in Fig. 1. The results
obtained with each method were compared using the criteria described
in the ISO 16140:2003, the NordVal guidelines and the AFNOR technical
board listed thirteen practicability criteria (AFNOR, 2013; ISO, 2003;
NordVal, 2009).
According to ISO 16140:2003 at least three levels of contamination
should be tested. In this study, four levels were analysed (D-6 to D-9).
They were spiked on four different swabs. Four independent analyses
of these four swabs were performed for each tested bacteria. As the
ISO 16140:2003 requires at least six repetitions, the dilution identified
as relative detection level with each individual detection method was
re-analysed with six swabs.
This ISO also requires the use of twenty samples to validate a system
on a food category, with 50% positive and 50% negative samples. The
same samples should be analysed by both the alternative and the reference methods. In this study, twenty samples were prepared presenting
different spike concentrations and samples were inoculated with one or
both targets (Salmonella spp. and Listeria spp.) of the complete CoSYPS
Path Food workflow (Table 2): i) five samples containing none of the
targets were used as negative samples; ii) six samples contained only
one of the targets at the LOD, ten times or hundred times above the
LOD; iii) one sample contained both targets at the LOD; iv) four samples
contained one target at the LOD and the other target ten or hundred
times above the LOD; v) two samples contained one target ten times
above the LOD and the other target hundred times above the LOD; vi)
one sample contained both targets ten times above the LOD and vii)
one sample contained both targets hundred times above the LOD.