The aim of the present study was to investigate the effect of Lactobacillus plantarum (L. plantarum) on the
growth performance as well as to assess the impact of probiotics L. plantarum on the expression of immunerelated
genes in the liver of tilapia fish (Oreochromis niloticus). Lactobacillus plantarum was administered
orally at 10⁶ CFU g⁻¹ feed to fish for 30 days. Thirty days after the start of the feeding period, fish were I/P
challenged with pathogenic Pseudomonas fluorescens (0.1 ml of 107 cells / ml).Only the fish fed the diet
containing L. plantarum showed significantly (P < 0.05) improved growth rates, protection against
Pseudomonas fluorescens compared to the control. Subsequently, real-time PCR was employed to determine the
mRNA levels of IL-6 TNF-α in the liver, of the control and L. plantarum groups. IL-6 and TNF-α gene
expression were significantly up-regulated by L. plantarum. Moreover, the mRNA levels of IL-6and TNF-α
were significantly higher in the L. plantarum group after P. fluorescens infection, suggesting that L. plantarum
can stimulate the immune response of Oreochromis niloticus.