Effect of autochthonous lactobacilli on immunologically important molecules of rainbow trout after bacterial infection studied on intestinal primoculture

Nowadays, the aquaculture industry is one of the fastest growing industries. Intensive aquaculture has a negative impact on fish health. Probiotic bacteria are often used due to beneficial effect to health of host, e.i. decrease of diseases outbreaks, immunomodulatory effect or better utilization of feed. The aim of this work was to study the influence of probiotic bacteria on the immune response of trout intestinal cells in primoculture infected with pathogenic bacteria. In the experiment, we tested the effect of pre-treatment of intestinal cells with an autochthonous strain of Lactobacillus plantarum R2 Biocenol™ (CCM 8674) following infection with the most serious salmonid pathogens – Aeromonas salmonicida subsp. salmonicida (CCM 1307) and Yersinia ruckeri (CCM 6093). Tested probiotic strain reduced inflammation after A. salmonicida infection through decreased expression of pro-inflammatory cytokines and increased expression of anti-inflammatory cytokines. In contrast, after infection with Y. ruckeri, which causes immunosuppression, the probiotic strain stimulated immunity by up-regulation of expression of proinflammatory cytokines and suppressed the expression of anti-inflammatory cytokines. These results are a prerequisite for the immunomodulatory potential of the strain, but its action must be confirmed in subsequent in vivo experiments. •Introduction of a new modified method for the preparation of primary culture of trout intestinal cells.•Testing the effect of probiotic autochthonous – L. plantarum R2 on immunologically important molecules gene expression.•L. plantarum R2 activates an anti-inflammatory answer in the gut cells infected with Aeromonas salmonicida.•L. plantarum R2 initiates a pro-inflammatory answer in the gut cells infected with immunosuppressive Yersinia ruckeri.