# Latilactobacillus sakei strains protect crucian carp against Aeromonas hydrophila–induced intestinal injury in an oral challenge model

## TL;DR

This study shows that certain Latilactobacillus sakei strains protect crucian carp from intestinal damage caused by a harmful bacteria, offering a potential alternative to antibiotics in aquaculture.

## Contribution

The study demonstrates the protective effects of specific L. sakei strains against Aeromonas hydrophila in crucian carp, highlighting their potential as probiotics in aquaculture.

## Key findings

- L. sakei strains JO12, JO26, and JO35 reduced intestinal inflammation and barrier damage in crucian carp.
- JO35 showed the best improvement in growth and feed efficiency and enhanced intestinal immunity.
- Strain-specific effects were observed, with JO35 regulating phagolysosomal competence and IgA barrier.

## Abstract

In aquaculture, the overuse of antibiotic could lead to antimicrobial resistance and destabilize host–microbiota homeostasis. Latilactobacillus sakei, belonging to the genus Latilactobacillus, was included in the list of bacteria that could be used in food in China in 2014. Increasing evidence demonstrated that its antagonistic capacity against a broad spectrum of pathogenic bacteria, indicating its promising potential for application in aquaculture. In this study, the protective effect of three L. sakei (JO12, JO26, JO35), isolated from the intestine of fish and shrimp, on mucosal injury caused by Aeromonas hydrophila in crucian carp under an oral challenge model was investigated. The result showed that compared with LGG, all three L. sakei strains alleviated A. hydrophila induced intestinal barrier damage and inflammation (downregulated intestinal TNF-α/IL-1β, upregulated IL-10, and reduced MyD88) in crucian carp. L. sakei JO35 delivered the greatest improvement in growth and feed efficiency. Compared with the model group, L. sakei JO26 and JO35 significantly decreased the levels of serum acid phosphatase (ACP) and increased intestinal lysozyme, whereas L. sakei JO12 lowerd serum ACP but exacerbated the elevation of intestinal AKP. Microbiome and transcriptome analysis revealed that the protective effect of L. sakei may be associated with the strain’s intestinal colonization capacity and its regulation of phagolysosomal competence (lysosome/phagosome, LAMP) and IgA barrier via pIgR (prominent with JO35).