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

In aquaculture, the overuse of antibiotic could lead to antimicrobial resistance and destabilize host-microbiota homeostasis. <i>Latilactobacillus sakei,</i> belonging to the genus <i>Latilactobacillus,</i> 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 <i>L. sakei</i> (JO12, JO26, JO35), isolated from the intestine of fish and shrimp, on mucosal injury caused by <i>Aeromonas hydrophila</i> in crucian carp under an oral challenge model was investigated. The result showed that compared with LGG, all three <i>L. sakei</i> strains alleviated <i>A. hydrophila</i> induced intestinal barrier damage and inflammation (downregulated intestinal TNF-<i>α</i>/IL-1β, upregulated IL-10, and reduced MyD88) in crucian carp. <i>L. sakei</i> JO35 delivered the greatest improvement in growth and feed efficiency. Compared with the model group, <i>L. sakei</i> JO26 and JO35 significantly decreased the levels of serum acid phosphatase (ACP) and increased intestinal lysozyme, whereas <i>L. sakei</i> JO12 lowerd serum ACP but exacerbated the elevation of intestinal AKP. Microbiome and transcriptome analysis revealed that the protective effect of <i>L. sakei</i> 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).