Optimizing Aeromonas hydrophila vaccine efficacy in common carp: The role of free vs. microencapsulated Lactiplantibacillus plantarum and Lactobacillus delbrueckii bulgaricus.

2026-01
Fish & shellfish immunology 168

PubMed: 41238066
DOI: 10.1016/j.fsi.2025.110996

Study Design

Sample size: n = 540
Population: A total of 540 fish (mean weight: 48 ± 5.1 g) ... common carp (Cyprinus carpio)
Methods: The effects of two probiotics, Lactiplantibacillus plantarum and Lactobacillus delbrueckii bulgaricus, administered orally either in free form or microencapsulated with alginate/chitosan, on the immunogenicity and protective efficacy of an Aeromonas hydrophila vaccine were investigated; fish were randomly allocated into six experimental groups and analyzed on days 0, 30, and 60, then challenged with A. hydrophila on day 60 and mortality monitored for 14 days.

Animal Study

This study investigated the effects of two probiotics, Lactiplantibacillus plantarum (L. plantarum) and Lactobacillus delbrueckii bulgaricus (L. bulgaricus), administered orally either in free form or microencapsulated with alginate/chitosan, on the immunogenicity and protective efficacy of an Aeromonas hydrophila vaccine in common carp (Cyprinus carpio). A total of 540 fish (mean weight: 48 ± 5.1 g) were randomly allocated into six experimental groups: vaccinated control (A), vaccinated + free L. plantarum (B), vaccinated + encapsulated L. plantarum (C), vaccinated + free L. bulgaricus (D), vaccinated + encapsulated L. bulgaricus (E), and unvaccinated control (F). Growth indices, immunohematological parameters, intestinal enzyme activity, antioxidant status, and serum biochemistry were analyzed on days 0, 30, and 60 of the experiment. On day 60, each group was challenged with A. hydrophila, and mortality was monitored for 14 days. The results demonstrated that fish receiving encapsulated probiotics (Groups C and E) exhibited significantly higher survival rates compared with the other groups, along with markedly improved growth performance (FCR, SGR, PER, FER) and intestinal enzyme activity (lipase, protease, amylase, ALP). Probiotic-supplemented groups showed significantly enhanced immune responses, evidenced by increased antibody titers, lysozyme activity, nitroblue tetrazolium (NBT) reduction, complement activity, globulin concentrations, and myeloperoxidase activity (P < 0.05). These immunological enhancements occurred without significant changes in hematological parameters or serum biochemical profiles, which remained statistically similar across groups (P > 0.05). Mortality following the challenge was lowest in Groups C and E (20 % vs. 80 % in the control group). In conclusion, microencapsulated L. plantarum and L. bulgaricus enhanced vaccine efficacy and immunogenicity more effectively than free probiotics. Alginate/chitosan encapsulation is therefore recommended as an efficient delivery system to optimize probiotic supplementation and vaccine performance in carp aquaculture.

Research Insights

Supplement	Dose	Health Outcome	Effect Type	Effect Size	Source
Lactobacillus bulgaricus & Lactobacillus plantarum	—	Improved Digestive Enzyme Activity	Beneficial	Moderate	View source along with markedly improved growth performance ... and intestinal enzyme activity (lipase, protease, amylase, ALP)
Lactobacillus bulgaricus & Lactobacillus plantarum	—	Improved Growth Performance	Beneficial	Moderate	View source fish receiving encapsulated probiotics (Groups C and E) exhibited significantly higher survival rates compared with the other groups, along with markedly improved growth performance (FCR, SGR, PER, FER)
Lactobacillus bulgaricus & Lactobacillus plantarum	—	Improved Immune Function	Beneficial	Moderate	View source Probiotic-supplemented groups showed significantly enhanced immune responses, evidenced by increased antibody titers, lysozyme activity, nitroblue tetrazolium (NBT) reduction, complement activity, globulin concentrations, and myeloperoxidase activity
Lactobacillus bulgaricus & Lactobacillus plantarum	—	Improved Vaccine Efficacy	Beneficial	Large	View source microencapsulated L. plantarum and L. bulgaricus enhanced vaccine efficacy and immunogenicity more effectively than free probiotics
Lactobacillus bulgaricus & Lactobacillus plantarum	—	Reduced Mortality	Beneficial	Large	View source Mortality following the challenge was lowest in Groups C and E (20 % vs. 80 % in the control group)