Scientists found that a common gut bacterium, Bifidobacterium longum, can protect tiny worms from harmful Salmonella and Shigella infections by making the gut more acidic and possibly releasing special proteins, while also calming down some of the worm’s immune signals. However, this study doesn’t involve IGF‑1 or give any direct tips for longevity or performance, so it isn’t useful for IGF‑1‑focused biohackers.

Salmonellosis and shigellosis remain major global health concerns, with <i>Salmonella</i> Typhimurium and <i>Shigella flexneri</i> classified as high-priority antibiotic-resistant pathogens by the World Health Organization. The development of new antibiotics is slow and challenging, underscoring the need for alternative therapeutic strategies. One promising approach involves leveraging gut microbiota-derived bacteria that confer colonization resistance against enteric pathogens. In this study, we screened a human gut microbiota culture collection and identified <i>Bifidobacterium longum</i> as the most effective species in inhibiting <i>S</i>. Typhimurium and <i>S. flexneri in vitro</i>. To evaluate its protective potential <i>in vivo</i>, we utilized <i>Caenorhabditis elegans</i> as a model system. Our findings demonstrate that <i>B. longum</i> significantly reduced pathogen burden and enhanced host survival following infection. Mechanistic analysis revealed that <i>B. longum</i> inhibits <i>S</i>. Typhimurium primarily through acidification, while <i>S. flexneri</i> suppression appears to involve a protein-mediated or heat-stable metabolite-dependent mechanism. Additionally, <i>B. longum</i> modulated host immune pathways, downregulating genes associated with the p38 MAPK and insulin/IGF-1 signaling pathways. These results highlight the potential of <i>B. longum</i> as a non-antibiotic therapeutic for controlling <i>Salmonella</i> and <i>Shigella</i> infections. However, further validation in mammalian models is required to assess its clinical relevance. Gut infections caused by <i>Salmonella</i> and <i>Shigella</i> are major global health threats. As an alternative to novel drug discovery, which is time-consuming and faces several challenges, this study explores the potential of gut bacteria to protect against these pathogens. We identified <i>Bifidobacterium longum</i>, a common gut microbe, which can significantly reduce infection by both <i>Salmonella</i> and <i>Shigella</i> in a lab setting and in a simple animal model. The bacterium functions by creating an environment that is hostile to pathogens and by modulating the host's immune responses. These findings suggest that <i>B. longum</i> could be developed as a natural, non-antibiotic treatment to control or reduce these enteric pathogen infections. This approach opens the door to using probiotics as effective tools in the global fight against antibiotic resistance.