article · Frontiers in Marine Science
Waterborne toxins such as deltamethrin and bacterial infections caused by Aeromonas hydrophila threaten aquatic animal health by triggering oxidative stress, inflammation, and immunosuppression. This laboratory trial evaluated whether incorporating the probiotic Lactobacillus plantarum, specifically strain LP20, at fifty milligrams per kilogram into Nile tilapia diets could counter these effects. Juvenile fish were assigned across control, pesticide-exposed, probiotic-fed, and combined groups over thirty days before being challenged with Aeromonas hydrophila. Exposure to deltamethrin reduced survival and disrupted blood biochemistry, while raising markers of liver damage and kidney strain. In contrast, dietary supplementation with Lactobacillus plantarum improved survival, elevated immune and antioxidant enzyme activities, and reduced tissue damage across the liver, spleen, gills, and intestine. The probiotic also enhanced the expression of key antioxidant genes. Overall, the feed additive mitigated physiological disruption, immunosuppression, and tissue inflammation caused by combined toxin exposure and bacterial infection.
Aquaculture operations face simultaneous pressures from environmental pollutants and bacterial diseases, which diminish fish welfare and productivity. Understanding how dietary probiotics such as Lactobacillus plantarum bolster immune defences and antioxidant capacity provides valuable insight into improving fish resilience against dual chemical and biological threats, supporting healthier stock management in fish farming environments without relying on synthetic chemicals.
This research demonstrates the potential of Lactobacillus plantarum as a functional feed additive for aquafeed manufacturers and fish farmers seeking to improve juvenile Nile tilapia resilience to combined waterborne toxins and bacterial pathogens. Tested in a controlled laboratory aquarium trial, the intervention represents early-stage applied research that requires validation in commercial-scale production systems, cost-benefit analysis, and shelf-life assessments before integration into commercial feed formulations.
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Aeromonas hydrophila infection is one of the major diseases that cause inflammation and immunodepression in aquatic animals. Likewise, waterborne toxins are known for their negative impact on the immunity and antioxidant responses of aquatic organisms. In this study, Lactobacillus plantarum (LP20) was incorporated in Nile tilapia, Oreochromis niloticus , diets (50 mg/kg) to investigate its role in the antioxidant capacity, immunity, and anti-inflammation induced by deltamethrin (DLM) toxicity (96-h LC 50 was 14.9 μg/L) and A. hydrophila (LD 50 , 2 × 10 8 CFU/ml). One hundred and twenty healthy fish with an initial weight of 28.21 ± 1.34 g were allotted in 12 glass aquaria (60 L) and divided randomly into four groups (triplicates, 10 fish per aquarium). The control fish neither received LP20 nor were exposed to DLM. The second group of fish was fed the control diet and subjected to DLM (DLM group). The third group of fish was provided with LP20 without DLM toxicity (LP20 group), and the fourth group of fish was fed LP20 and subjected to DLM (DLM + LP20 group). After 30 days, fish were intraperitoneally injected with A. hydrophila . Ten days post infection, the survival rate was lower in fish exposed to DLM than those exposed to LP20. Further, fish fed on LP20 had elevated serum total protein (sTP), albumin (ALB), globulin (GLB), phagocytic index (PI), phagocytic (PA), and lysozyme activities (LZM), but they had lower urea, uric acid bilirubin, creatinine, glucose, aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT) activities after 24 h, 48 h, and 1 week post A. hydrophila challenge. However, fish exposed to DLM had lower sTP, ALB, GLB and higher urea, uric acid, bilirubin, creatinine, glucose, ALT, AST, and ALP after 24 h, 48 h, and 1 week post A. hydrophila challenge. Markedly, after the A. hydrophila challenge, fish exposed to DLM + LP20 displayed upregulated levels of superoxide dismutase ( SOD ), catalase ( CAT ), and glutathione peroxidase ( GPx ) genes. The transcription of interferon gamma ( IFN- γ), interleukin 12 ( IL-12 ), and tumor necrosis factor alpha ( TNF- α) was upregulated in DLM and DLM + LP20 groups. Fish exposed to DLM downregulated interleukin 8 ( IL-8 ) gene expression after A. hydrophila challenge. Further, fish displayed upregulation of heat shock protein 70 ( HSP70 ) gene expression after DLM toxicity. Besides, fish exposed to DLM toxicity and A. hydrophila infection had severe inflammatory features in the liver, spleen, gills, and intestine, while dietary LP20 relieved the inflammatory features. In summary, dietary LP20 relieves Nile tilapia from oxidative stress, immunosuppression, and inflammation induced by DLM and A. hydrophila infection.
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DOI: 10.3389/fmars.2021.621558
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