Friend for the host foe for the guest: Evidence from probiotic <i>Lactobacillus rhamnosus</i> GG

The human-derived probiotic <i>Lactobacillus rhamnosus</i> GG (LGG) improves intestinal health in humans. However, in zebrafish, the SpaC pilin of LGG and the LPS produced by SpaC-induced dysbiotic gut microbiota cause intestinal pyroptosis and epithelial damage. This negative effect is host-specific, raising concerns about the safety of using classical terrestrial-derived probiotics strains in aquatic species. These results emphasize the need for species-specific probiotic evaluations and promote the regulation of non-host origin probiotics in aquaculture. Further research is needed to understand the action mechanisms of non-host probiotics and their impacts on economical fish species.