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¹ IPB University, Graduate Program of Aquaculture Science, Faculty of Fisheries and Marine Science
² IPB University, Departement of Aquaculture, Faculty of Fisheries and Marine Science DOI : 10.4194/AQUAST2919 Viewed : 97 - Downloaded : 93 Intensive farming systems in tilapia (Oreochromis niloticus) increase susceptibility to Aeromonas hydrophila infection, which compromises fish health and survival. This study investigated immune gene expression (IL-1β and LYSC) and non-specific immune responses in four black tilapia strains—MAG NIN, BIG NIN, GIFT, and SAKTI—following bacterial challenge. A completely randomized design with five treatments and five replications was employed. Fish were intramuscularly injected with A. hydrophila at the LD₅₀ dose of 10⁶ CFU mL⁻¹ (0.1 mL/fish). Data were analyzed by ANOVA at a 95% confidence level, followed by Duncan’s test. Results revealed that the SAKTI strain demonstrated the highest resistance, achieving a significantly greater survival rate (53%) compared with other strains (P<0.05). This superior resistance corresponded with enhanced non-specific immunity, as indicated by phagocytic activity that increased until day 14 (52%) and lysozyme levels that peaked at day 7 (0.18±0.00). Additionally, SAKTI tilapia exhibited stable expression of IL-1β (2.0±0.15) and LYSC (- 1.2±0.01), unlike the pronounced decline observed in BIG NIN and MAG NIN. These findings suggest that the SAKTI strain holds potential as a genetic resource for selective breeding programs aimed at improving resistance to A. hydrophila infection in tilapia aquaculture. Keywords : Aeromonas hydrophila Gene expression Immune response Tilapia