AimsEvaluation of the efficacy of marine lactic acid bacteria, Lactobacillus plantarum AH 78, on growth performance and immune response of Nile tilapia (Oreochromis niloticus) challenged with Aeromonas hydrophila. Methods and ResultsMarine probiotic, Lact.plantarum AH 78, was incorporated in Nile tilapia diets at 00, 05, 10 or 20% (w/w). The diets were fed to juvenile Nile tilapia for 40days, after which they were challenged with pathogenic bacterium, Aer.hydrophila. The best growth rates and feed efficiency were obtained at 05% probiotic, while fish survival was not affected by dietary probiotic. After challenge with Aer.hydrophila immunological responses and survival were recorded at 10% probiont. Likewise, significant up-regulation of the expression of cytokine genes, IL-4, IL-12 and IFN-, in fish livers was found at 10% probiont, compared to the control diet. Concomitantly, AH 78 colonized the intestinal mucosa of treated fish, even after reverting to the control diet, and remained viable in the feed stored at 4 degrees C up to 12months. ConclusionsMarine Lact.plantarum AH 78 at 05-10% inclusion level conferred the best performance and immune response of Nile tilapia challenged with Aer.hydrophila. Significance and Impact of the StudyMarine Lact.plantarum AH 78 could be considered as a potential probiotic to control disease outbreaks in farmed Nile tilapia.