Citrulline-enhanced chicken resistance to Salmonella Enteritidis infection via urea cycle modulation and nitric oxide production.

Salmonella Enteritidis infection has caused substantial economic losses in the poultry industry. Traditional antibiotic treatments have led to issues, such as drug-resistant bacteria and antibiotic residues, which pose significant threats to human and animal health, as well as food and environmental safety. Therefore, establishing new, effective prevention and control methods is of paramount importance. In this study, we utilized gas chromatography-mass spectrometry (GC-MS) metabolomics to analyze the metabolomic profiles of chickens infected with varying concentrations of Salmonella Enteritidis. Significant differences in the metabolomes were observed, with citrulline identified as a candidate biomarker, showing increased levels corresponding to higher infection doses. Exogenous addition of citrulline was found to upregulate the expression of the inducible nitric oxide synthase (iNOS) gene in the urea cycle of chicken HD11 macrophages, leading to increased nitric oxide (NO) levels and enhanced phagocytosis of Salmonella Enteritidis by HD11 cells. Furthermore, in vivo challenge experiments demonstrated that exogenous citrulline improved the ability of chickens to clear Salmonella Enteritidis and increased their survival rate post-infection. Importantly, this effect could be attenuated by the iNOS inhibitor 1400W. Thus, our study presents a novel strategy for combating bacterial infections through metabolic modulation. IMPORTANCE: Chickens respond to Salmonella infection by adjusting the metabolic state of their bodies. Citrulline can enhance the phagocytic ability of phagocytes by strengthening the urea cycle. In vitro clinical trials have revealed that citrulline can increase the survival rate of chickens after Salmonella infection.