2. Universidad Cardenal Herrera-CEU

Salmonellosis remains one of the main foodborne zoonoses in Europe, with poultry products as the main source of human infections. The slaughterhouse has been identified as a potential source for Salmonella contamination of poultry meat. Despite the mandatory programme of the EU, there are companies with persistent Salmonella that are unable to remove the bacteria from their processing environment, compromising the entire production line. In this context, an intensive sampling study was conducted to investigate a slaughterhouse with persistent Salmonella problems, establishing the genetic relationship among Salmonella strains isolated during the slaughter process. A total of 36 broiler flocks were sampled during processing at the slaughterhouse. Salmonella was identified based on ISO 6579-1:2017 (Annex D), serotyped by Kauffman-White-Le-Minor technique, and the genetic relationship was assessed with ERIC-PCR followed by PFGE. The outcomes showed that 69.4% of the batches sampled carried Salmonella upon arrival at the slaughterhouse and that 46.3% of the different samples from carcasses were contaminated with Salmonella. The two serovars isolated at the different steps in the slaughterhouse were Enteritidis (98.2%) and Kentucky (1.8%). Pulsed-field gel electrophoresis analysis revealed a low genetic diversity, with all S. Enteritidis isolates showing a nearly identical pulsotype (similarity >85%) and S. Kentucky strains showed the same XbaI PFGE profile (95.0% genetic similarity). The results of this study showed a high genetic relationship among isolates recovered from carcasses and environmental samples in the slaughterhouse from both Salmonella-positive and Salmonella- free flocks. Salmonella strains re-circulated across to poultry flocks and re-entered the slaughterhouse to survive on the processing line. Thus, it is necessary to implement molecular diagnosis methods in time at the field level to determine the Salmonella epidemiology of the flock, to make rapid decisions for the control of Salmonella and prevent entry into the slaughterhouse environment.

Salmonella and Campylobacter have been widely recognized as most important zoonotic pathogens with economic impact in animals and humans. Handling or consumption of contaminated poultry meat is considered the most common sources of both human infections. In this sense, the legislators have been working to limit Salmonella and Campylobacter presence; however, high number of salmonellosis and campylobacteriosis are continued declare. In order to lower the risk for human infections, most studies have been focused on the farm level to reduce the number of flocks colonized with these bacteria. Nevertheless, it has been reported that, after processing, carcasses are contaminated even when the flocks are Salmonella or Campylobacter negative at the farm. Therefore, it is necessary to introduce additional treatments to control or inhibit the survival and potential growth of both pathogens in chicken meat. In this context, the aim of this Thesis is to study the Salmonella and Campylobacter contamination of poultry carcasses during the slaughter process and evaluate different modified atmospheres packaging against the main strain isolated at slaughter level.