Triploid Cyprinid Fish (TCF) Under Aeromonas sp. AS1-4 Infection: Metabolite Characteristics and In Vitro Assessment of Probiotic Potentials of Intestinal Enterobacter Strains

TL;DR

This study explores how a harmful bacteria, Aeromonas sp. AS1-4, affects fish and identifies beneficial intestinal bacteria that could help manage fish health in aquaculture.

Contribution

The study identifies and characterizes potential probiotic Enterobacter strains with anti-pathogenic properties in triploid cyprinid fish.

Findings

Aeromonas sp. AS1-4 infection causes oxidative damage and alters amino acid metabolism in fish.

Three Enterobacter strains show strong probiotic traits, including biofilm inhibition and antioxidant activity.

The identified probiotics coaggregated with pathogens and suppressed their harmful effects.

Abstract

Our research found that Aeromonas sp. AS1-4 infection could induce severe oxidative damage in the liver and spleen of TCFs, along with a significant alteration of amino acid metabolism. Following this, we identified three probiotic isolates displaying anti-pathogenic capability and potential traits in vitro. This study provided a valuable insight into exploring the pathogenic mechanism and guiding the probiotic application in aquaculture practices.

The majority of Aeromonas strains are opportunistic pathogens for both humans and animals, causing a variety of diseases and posing a considerable risk to their health. In the current study, triploid cyprinid fish (TCF) were infected with a novel pathogenic Aeromonas sp. AS1-4 for pathological analysis. TCFs receiving Aeromonas sp. AS1-4 challenge exhibited oxidative damage in the liver and spleen, along with significant changes in immune-related gene expressions. Metabolomics assay indicated that strain AS1-4 challenge may exhibit a significant impact on metabolic processes of amino acids, with methylsuccinic acid (MSA) identified as vital biomarker. Following that, three potential probiotics designated Enterobacter strains fkY27-2, fkY84-1 and fkY84-4 were isolated from the intestine of TCFs, displaying excellent safety characteristics. In addition, intestinal Enterobacter strains exhibited multiple probiotic traits, including high degrees of hydrophobic activity, aggregation performance, biofilm-forming activity (BFA) and nutrient decomposing ability. Moreover, these probiotic isolates markedly coaggregated with Aeromonas sp. AS1-4 and Edwardsiella tarda 1l-4 and then suppressed their pathogenic biofilm-forming abilities, along with possessing robust antioxidant potential against various free radicals. These findings may provide valuable insights into metabolic response in fish post infection and health management in aquaculture.

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