Effect of Two Limosilactobacillus Strains and Salmonella Challenge on Immune Markers in a Poultry Caecal Model

Probiotic microorganisms are increasingly investigated for their capacity to influence host physiology, particularly through interactions with the intestinal immune system. The present study aimed to assess the effects of selected probiotic strains, Limosilactobacillus reuteri CCM 9425 and Limosilactobacillus reuteri B2/6, applied simultaneously in an ex vivo model of poultry caecal explants, with a focus on their impact on immune-related gene expression. In addition to probiotic treatment, explants were challenged with Salmonella Enteritidis PT4 to evaluate immune responses under infectious conditions and following probiotic pre-treatment. The transcriptional profiles of selected cytokines (IL-15, IL-1β, IL-8, and IL-18) indicated that probiotic exposure did not trigger an exaggerated inflammatory response. Instead, a consistent and significant increase in IL-15 expression was observed in both the probiotic-treated group and the group receiving probiotic pre-treatment (p < 0.01). The upregulation of IL-15, a cytokine involved in early immune defense and activation of innate immune cells, may reflect enhanced immune readiness without accompanying tissue damage. Taken together, these findings demonstrate that the investigated probiotic strains can modulate intestinal immune responses in a controlled manner, supporting gut homeostasis while avoiding harmful inflammation.