Virginia Tech researchers reported prophylactic phage therapy that protects mice against subsequent oral Salmonella infection. The approach engineers a nonpathogenic E. coli “prophage-encoding” bacterium to produce an obligately lytic phage targeting Salmonella enterica Typhimurium (STm), with the concept framed around pre-positioning phage activity before exposure. In a Nature Microbiology study, the engineered bacterium colonized the gut, produced high levels of lytic phage, and improved survival after later STm challenge. The team also reported reduced intestinal pathogen colonization. Investigators said the results demonstrate proof of concept for enteric infection strategies where conventional phage therapy can struggle, using an engineered gut-resident system rather than relying solely on post-exposure phage dosing.