Dietary supplementation of Priestia sp. PPB30 attenuates intestinal colonization and inflammatory response induced by Aeromonas veronii in loach through interfering with the LuxS/AI-2 quorum sensing system.

Aeromonas veronii, a zoonotic opportunistic pathogen, has posed serious threats to both the aquaculture industry and human health. The quorum sensing (QS) system plays a crucial regulatory role in the expression of virulence factors in A. veronii. Quorum sensing inhibitors (QSIs) provide an alternative control method by disrupting bacterial QS-systems, thereby reducing pathogenicity and virulence without directly killing bacteria. This study primarily explored the interference effect of Priestia sp. PPB30 on the LuxS/AI-2 QS system of A. veronii Z12 and its impact on virulence factors. Screening through a bioluminescence assay revealed that strain PPB30 effectively reduced the levels of autoinducer-2 (AI-2) in A. veronii Z12 without affecting its growth. Following treatment with strain PPB30, significant changes in the expression of LuxS/AI-2 related genes in strain Z12 were observed, along with a reduction in biofilm formation and the expression of virulence factors, including adhesion, hemolysis, extracellular proteases, and motility. Moreover, strain PPB30 reduced the colonization of A. veronii Z12 in the intestines of loaches, but had no inhibitory effect on the colonization level of the LuxS/AI-2 system-deficient mutant strain Z12ΔluxS in the loach intestine. Additionally, we found that dietary supplementation with strain PPB30 effectively alleviated intestinal damage caused by A. veronii Z12 infection and mitigated the host' s inflammatory response. The research findings reveal that Priestia sp. PPB30, as a potential probiotic, offers a novel strategy for the prevention and control of aquaculture pathogens by disrupting the LuxS/AI-2 QS-system, thereby inhibiting the expression of virulence and intestinal colonization of A. veronii Z12.