McMaster University researchers reported a precision bacteriophage therapy that neutralizes adherent-invasive E. coli (AIEC) linked to Crohn’s disease inflammation in a mouse model. The team used phages to reduce AIEC virulence without broadly disrupting the gut microbiome. The study, published in Science Translational Medicine, also showed the phage intervention improved response to low-dose corticosteroids, suggesting a potential path to reduce steroid exposure while maintaining efficacy. A key element is the approach’s selectivity—targeting a difficult-to-pinpoint microbial driver rather than relying on broad-spectrum antibiotics during flares. The work strengthens the case for microbiome “cause targeting” strategies in inflammatory bowel disease, where precision therapies could address underlying drivers and potentially improve long-term outcomes.