Behavior of surface contamination by Salmonella spp. on broiler carcasses during slaughter stages

Salmonella spp. is a globally relevant pathogen frequently associated with foodborne infections and poultry products. This study aimed to evaluate the occurrence and quantification of Salmonella spp. during different stages of the broiler slaughter process and to assess the association of processing stages with reductions in contamination levels. The study was conducted in a federally inspected broiler slaughterhouse in Paraná, Brazil. A total of 2,100 analyses were performed on chicken carcasses collected at seven points along the slaughter line over 20 weeks. Salmonella detection followed the ISO 6579:2017 methodology, while quantification was performed using the miniaturized most probable number (mMPN) method with molecular confirmation by the invA gene. Subsequently, 211 isolates were serotyped, and 97 Salmonella Heidelberg isolates were analyzed by pulsed-field gel electrophoresis (PFGE). The highest occurrence of Salmonella spp. was observed at the pre-scalding stage (N = 236/78.66%). Significant reductions in Salmonella counts were observed after the scalding stage, after the post-evisceration critical control point for removal of visibly contaminated carcasses (CCP 1B), and after final washing before chilling (P < 0.05). Five serovars were identified, with Salmonella Heidelberg predominating (N = 193/91.5%). PFGE analysis revealed high genetic similarity (90%) among isolates, with highly similar profiles identified at different slaughter stages and sampling weeks. These findings demonstrate that Salmonella spp. was detected throughout the slaughter process, although reductions in contamination levels were observed at specific processing stages. In addition, the detection of highly similar isolates at different sampling points and weeks contributes to the understanding of Salmonella contamination dynamics in poultry slaughterhouses.