The Detection of Salmonella Enteritidis on German Layer Farms after Cleaning and Disinfection

SIMPLE SUMMARY: Salmonella is a common bacterium that can cause foodborne illness in humans. Testing poultry for Salmonella helps us identify contaminated products and prevents them from reaching consumers, reducing the risk of outbreaks and protecting public health. This study aimed to assess the occurrence of Salmonella carry-over between successive flocks of laying hens using established testing techniques. A Salmonella prevalence rate of 25% in the samples after cleaning and disinfection (C&D) indicates areas for improvement in C&D procedures during the service period. The study found that infectious Salmonella (specifically Salmonella Enteritidis) can persist for a long time in floor-reared production systems, which are easier to clean than caged houses. It is crucial to implement thorough C&D procedures between cycles, assess cleanliness after C&D through targeted sampling before introducing new flocks, and consider the surroundings of poultry houses when implementing hygiene measures. By incorporating Salmonella testing into C&D practices, poultry producers can enhance overall hygiene protocols, prevent cross-contamination, reduce the risk of contamination, and maintain a safe environment for workers and consumers. ABSTRACT: The presence of Salmonella Enteritidis in poultry houses after cleaning and disinfection can pose a potential risk to public health, as Salmonella remains one of the most important causes of foodborne diseases. This study focused on ten German layer farms (including floor-reared and free-range systems) with a recent history of Salmonella Enteritidis, and samples were collected from July 2018 to March 2021 after the cleaning and disinfection process. A total of 244 swab samples were tested for the presence of Salmonella using real-time PCR, followed by a culture of positive samples. Results revealed that 61 out of the 244 swab samples tested positive for Salmonella, indicating a prevalence of 25% in the samples examined. Among the Salmonella-positive swab samples identified with the PCR assay, 65.6% (40 out of 61) were confirmed by the culture. Of the 40 isolates obtained from the culture, 36 were identified as Salmonella Enteritidis, while 4 were categorized as rough Salmonella strains. This study emphasizes the importance of both the surrounding area of the poultry houses in terms of infection carry-over and the meticulous implementation of cleaning and disinfection procedures to eliminate any remaining infection within the houses. To mitigate the risk of further Salmonella spread on layer farms, additional investigations are recommended to focus on the existing transmission pathways of Salmonella and their genetic diversity.