Analysis of ERIC-PCR genomic polymorphism of Salmonella isolates from chicken slaughter line

The chicken slaughter line is a source of cross-contamination of Salmonella. In this study, ERIC-PCR was applied to analyse the ERIC-PCR genomic polymorphism of Salmonella isolates from a commercial chicken slaughter line and to trace the route of contamination. Samples were collected from carcasses and contact surfaces at the points of post-evisceration, post-chilling and post-grading. The prevalence of Salmonella at the evisceration point was high but significantly decreased along the slaughter line. The ERIC-PCR fingerprints indicated that a total of seven groups were clustered, and the genotypic diversity of isolates progressively decreased along the slaughter line. By tracing the genotypic diversity, contact surfaces at post-evisceration were found to be the major contamination sources of Salmonella during chicken processing, since the genotype diversity of isolates from the post-evisceration point could be exactly matched to that from the post-chilling and post-grading points. Interestingly, three Salmonella strains were still detected after decontamination and washing; these three isolates having a strong capacity for attachment were able to produce biofilm on polystyrene surfaces. This study suggests that the evisceration point is the source of cross-contamination, with Salmonella isolates still present after washing procedure. Therefore, more effective measures must be undertaken to control the spread of Salmonella in such processing lines.