Effects of Lactobacillus fermentum administration on caecal cytokine expression and serum immunoglobulin concentration in Salmonella Infantis-challenged chickens

Abstract

Salmonella Infantis is one of the most predominant serovars of S. enterica in the poultry industry of Ecuador, where numerous multidrug resistant strains have been reported. Nevertheless, many immunological features related to this pathogen remain unknown. The use of probiotics rises as an emerging approach to mitigate gut colonization by pathogenic bacteria in chickens. This research aimed to assess the influences of S. Infantis infection on the expression of immune related genes (Interleukin-1β (IL1B), IL13, IL15, IL17, and MYD88) and on the serum immunoglobulin (IgA, IgM) levels in broiler chickens. Additionally, the same criteria were evaluated during the administration of Lactobacillus fermentum as a probiotic to evaluate its immunomodulatory properties. Two-hundred 1-day old broiler chickens were randomly assorted into four experimental groups as follows: (i) Control, with untreated chicken; (ii) Lf, treated with L. fermentum; (iii) Se, infected with S. Infantis; and (iv) LfSe, inoculated with both bacteria. Experiments were conducted for 15 days. Per group, serum and caecal samples were collected from eight and ten animals, respectively. Gene expression analysis was performed using RT-qPCR, while immunoglobulin levels were measured with ELISA. Results revealed that relative expression of these genes was not affected by any of the experimental treatments, as were the levels of IgA. The concentration of IgM, on the other hand, was augmented when animals were exposed to the probiotic before infection with S. Infantis. Although the mechanisms behind the effects remain unclear, the increased antibody production ascertains that the probiotic treatment with L. fermentum in S. Infantis infection favors the immune response in the gut of broiler chicken. Further research might elucidate the complex dynamics involved.