Prevalence and Characteristics of Salmonella spp. by Production Stage in Integrated Broiler Operations in Korea

Background Vertically integrated broiler production systems enable efficient poultry production but may facilitate the dissemination of Salmonella throughout the production chain. Objectives This study investigated the prevalence and characteristics of Salmonella at each stage of the production process of three major integrated broiler operations in Korea. Methods From 2022 to 2024, samples were collected from breeder hatcheries, broiler breeder farms, commercial broiler hatcheries and commercial broiler farms of three major integrated broiler operations in Korea. Salmonella isolates were characterized by serotyping, antimicrobial susceptibility testing, virulence gene profiling, pESI‐like plasmid detection, and pulsed‐field gel electrophoresis (PFGE). Results The prevalence of Salmonella was higher in commercial hatcheries (30.0%–45.0%) and commercial farms (17.6%–62.7%) than in breeder hatcheries (10.0%–30.0%) and breeder farms (3.3%–13.4%). In breeder and commercial farms, the prevalence increased during the rearing period. Seven Salmonella serovars were identified, and the predominant serovar was S . Infantis (22.2%). Interestingly, S . Infantis exhibited multidrug resistance in 96.8% of isolates and carried the pESI‐like plasmid in 97.6% of isolates. Among the 20 virulence genes tested, several genes were widely distributed among isolates, whereas sefA , sefC and spvC were exclusively detected in S . Enteritidis. In PFGE analysis, identical pulsotypes of S . Enteritidis and S . Infantis were found to be transmitted vertically from breeder hatcheries to commercial farms by operation. Conclusions These findings demonstrate that Salmonella is transmitted downstream throughout the production process, and therefore, critical strategies, including rigorous biosecurity, hygiene and monitoring across the entire production chain, are required to control Salmonella .