Bacterial dynamics and communities along two broiler slaughter lines in Norway

Good process hygiene in broiler slaughter is paramount to achieving safe products with long shelf-lives. Here we investigated changes in bacterial load and diversity on chicken carcasses at selected stages on slaughtering lines, using both quantitative methods and molecular analyses. The study was conducted in two broiler abattoirs in Norway, and carcasses from flocks that had been classified as either positive or negative for Campylobacter were used. In total, 120 neck-skins were collected at four sampling locations: before scalding, after plucking, after evisceration, and after chilling. The samples were analysed both qualitatively and quantitatively. To determine the composition of the entire microbial community, amplicon sequencing of the 16S rRNA gene was performed. The largest reduction of specific taxa (Enterobacteriaceae, E. coli, and Campylobacter) was observed after washing and chilling, especially where extended chilling (>3 h) was used. For TPC, a large reduction was also observed after scalding and plucking. Campylobacter-positive flocks had lower amounts of indicator bacteria at all sampling points. Scalding water samples had low amounts of E. coli and were negative for Campylobacter. The 16S rRNA amplicon sequencing results from 80 neck-skin samples displayed that the bacterial communities were more diverse early in the slaughter line, dominated by Staphylococcus, Escherichia-Shigella, and Streptococcus, but altered to a less-diverse community, dominated by Asinibacterium spp., Afipia spp., Pseudomonas, Polaromonas, and Psychrobacter after chilling. These results suggest that conditions along the slaughter line can be used as a predictor of neck skin bacterial communities. Bio-mapping of microbial indicators and better understanding of bacteria diversity during slaughter and chilling contribute to improvements in decision making for process hygiene, testing of interventions and corrective actions for food safety management.