Lactobacillus rhamnosus boosts immunity and survival in striped catfish (Pangasianodon hypophthalmus) via hmgb1 gene modulation against Aeromonas hydrophila infection

Abstract Background Probiotics are increasingly used in aquaculture to improve growth, enhance immune responses, and reduce antibiotic dependence. This study evaluated the effects of dietary Lactobacillus rhamnosus on growth performance, non-specific immunity, serum biochemical profiles, and disease resistance of striped catfish ( Pangasianodon hypophthalmus ) against Aeromonas hydrophila (ATCC 7966). A 45-day feeding trial was conducted using four groups (control and three probiotic treatments: 1 × 10⁸, 2.5 × 10⁸, and 5 × 10⁸ CFU/g feed), each in triplicate. Results Among the probiotic-fed groups, fish receiving 2.5 × 10⁸ CFU/g (T2) showed the best overall performance, with significantly improved growth and enhanced innate immune responses, including higher nitroblue tetrazolium (NBT) activity, lysozyme and myeloperoxidase (MPO) levels compared to the control ( P < 0.05). Probiotic supplementation also improved serum protein profiles, showing increased total protein, albumin, and globulin levels, and reduced serum glucose, SGPT, and SGOT levels relative to the control. Expression analysis revealed significant modulation of hmgb1 across examined tissues ( P < 0.05), with downregulation during probiotic feeding, whereas bacterial challenge induced upregulation in immune-related organs (kidney and spleen). In addition, probiotic-fed fish exhibited higher survival following A. hydrophila challenge. Conclusion Overall, dietary Lactobacillus rhamnosus at 2.5 × 10⁸ CFU/g feed showed comparatively better performance in enhancing growth, immunocompetence and resistance of P. hypophthalmus against A. hydrophila .