Abstract

Foodborne pathogens pose a major global health hazard, worsened by drug-resistant strains. Therefore, designing novel therapeutic strategies is crucial. Here, we identified the protective role of gut-commensal Odoribacter splanchnicus (OS) against Salmonella in mice by promoting colonization resistance, preserving gut barrier integrity, and preventing acute inflammation and biofilm formation. In vitro, both live O. splanchnicus (OS) and their culture supernatant inhibited Salmonella biofilm formation, intracellular proliferation in human intestinal cells, and virulence gene expression. Further, our results depicted that OSs protective role acts over a broad spectrum as it confers protection against Gram-positive, Listeria monocytogenes and Gram-negative, Salmonella Typhimurium. Notably, OS conferred protection even when administered post-infection in mice, highlighting its therapeutic potential. Using several biochemical and proteomics approaches, we characterized key OS-secreted molecules that limit intracellular Salmonella and Listeria replication in human intestinal epithelial cells by regulating key virulence effectors and flagella. Collectively, our study establishes OS as the broad-spectrum protective agent against Salmonella and Listeria infections, with promising therapeutic potential. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=93 SRC="FIGDIR/small/609322v3_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@6c017eorg.highwire.dtl.DTLVardef@d608d9org.highwire.dtl.DTLVardef@1df103aorg.highwire.dtl.DTLVardef@1a251d2_HPS_FORMAT_FIGEXP M_FIG C_FIG Author SummaryFoodborne pathogens such as Salmonella and Listeria continue to threaten global health, especially with the rise of antibiotic resistance. In this study, we identify the gut commensal bacterium Odoribacter splanchnicus (OS) as a potent protectant against these pathogens. Using a mouse model, we show that OS enhances colonization resistance, maintains gut barrier integrity, and prevents both inflammation and biofilm formation during infection. Remarkably, OS also limits pathogen proliferation and virulence gene expression in human intestinal cells. These protective effects are mediated by both live OS and its secreted molecules within culture supernatant. Importantly, OS administration post-infection also conferred protection, indicating strong therapeutic potential. Biochemical and proteomic analyses revealed OS-secreted factors that suppress key virulence and motility pathways in pathogens. Our findings establish Odoribacter splanchnicus as a promising broad-spectrum biotherapeutic agent against major foodborne infections.