Harnessing Native Swine Probiotics: Unveiling Their Protective Shield Against Salmonella Typhimurium – Insights from an Immune and Gut Microbiome Perspective

Probiotics confer strain-specific health benefits, including protection against pathogenic infections. This study evaluated the protective efficacy of single- and multi-strain probiotics against Salmonella Typhimurium in a mouse model. Mice were administered Lactiplantibacillus plantarum TBRC-15420, Bacillus amyloliquefaciens TBRC-15434, Saccharomyces cerevisiae TBRC-19857, or their combination for 30 days prior to S. Typhimurium challenge. Protective effects were assessed through survival rates, clinical symptoms, weight changes, pathogen clearance, histopathology, secretory IgA levels, and gut microbiota shifts using 16S rRNA sequencing. No mortality was observed; however, mice exhibited varying symptoms post-infection, with some recovering by day five. Probiotics mitigated weight loss, with the multi-strain combination being most effective, while L. plantarum TBRC-15420 provided the strongest single-strain protection. Probiotics enhanced secretory IgA levels, with B. amyloliquefaciens TBRC-15434 and L. plantarum TBRC-15420 eliciting robust immune responses. All strains effectively reduced S. Typhimurium levels in the small intestine and prevented its translocation to the liver and spleen, achieving complete bacterial clearance by day five. Probiotic pretreatment preserved the structural integrity of the intestine, liver, and spleen. It also promoted beneficial bacterial phyla such as Bacteroidetes and Firmicutes while suppressing Proteobacteria , thereby maintaining gut microbiome homeostasis during infection. These findings support probiotics as antibiotic alternatives for Salmonella infection management, emphasizing their role in immune modulation and microbiota stability.