The gut microbiota in Salmonella Typhi infection and translocation: Mechanisms of colonization resistance, pathogen...

The systemic establishment of the strictly human-adapted pathogen Salmonella Typhi critically depends on functional interplay between its virulence effectors and the host gut microbiome. Organized within a "colonization-toxicity-immunity- microecological intervention" framework, this review synthesizes recent molecular and multi-omics evidence to delineate key host-pathogen-microbiota dynamics. During colonization, a healthy gut microbiota exerts multi-layered colonization resistance through nutrient and niche competition, as well as via microbial metabolites such as short-chain fatty acids and secondary bile acids. Current evidence more consistently supports DDR-associated cellular senescence and type I IFN signaling as major outcomes of typhoid toxin activity; pyroptosis, if observed, appears context-dependent and should not be presented as a universal endpoint. Concurrently, the Vi capsule and type III secretion system (T3SS) effector proteins (e.g., SteD) act in concert to disrupt innate and adaptive immunity, reprogram the mucosal immunometabolic landscape, and exacerbate microbial dysbiosis. We also evaluate the strength of evidence and applicability of microbiota-targeted interventions, including probiotics, prebiotics, synthetic microbial consortia, and fecal microbiota transplantation (FMT), and address the limitations of extrapolating from Salmonella Typhimurium mouse models to human Salmonella Typhi, typhoid toxin infection. Furthermore, we emphasize the need for cross-validation using human intestinal organoids, humanized immune mice, and population-level data, integrated with metabolomic and immune profiling, to establish a definitive "metabolism-immunity-toxicity" causal chain. Confronting the persistent evolution of H58 and other drug-resistant lineages, we propose a paradigm shift through the convergence of genomic epidemiology, microbiota-informed risk stratification, and vaccine-microbiota synergism; these elements collectively chart an implementable roadmap for precision medicine in disease control.