Researchers at McMaster University in Canada have used bacteriophages to disarm a bacterium associated with Crohn’s disease, reducing gut inflammation and improving the response to corticosteroids in preclinical models. The study, published in Science Translational Medicine, targets adherent-invasive Escherichia coli (AIEC) strains isolated from patients with Crohn’s disease. This is laboratory and animal research; phage therapy for IBD has not yet been tested in human trials.
Background Context
Crohn’s disease is a chronic inflammatory bowel disease characterised by transmural inflammation that can affect any part of the gastrointestinal tract. The condition is strongly associated with dysbiosis, an imbalance in the composition and function of the gut microbiome. Current treatment strategies include immunosuppressive medications and biologics targeting specific inflammatory pathways, but many patients experience incomplete response or loss of response over time. The gut microbiome contains trillions of microorganisms, including bacteria, fungi, and viruses, with bacteriophages representing the most abundant viral component. These viruses specifically infect bacteria and can influence microbial community structure.
Key Findings
Bacteriophages are viruses that infect bacterial cells specifically, without harming human tissue. The McMaster team, drawing on the Verdu laboratory’s microbiome work and the Hosseinidoust laboratory’s expertise in targeted antimicrobials, applied them to AIEC strains isolated from people with Crohn’s disease.
The notable feature of the approach is that the phages did not kill the bacteria. Instead they attenuated their virulence, suppressing the molecular structure AIEC use to attach to the gut lining. One of the investigators likened it to knocking out a few of the bacterium’s teeth, leaving it present but far less able to cause damage. This differs from broad-spectrum antibiotics, which eliminate harmful and beneficial bacteria indiscriminately, and it avoids the selection pressure that comes from trying to kill the target outright.
In the experimental colitis models used, the intervention significantly reduced gut inflammation. The phages also enhanced the effect of corticosteroids: a lower-than-standard steroid dose combined with phage treatment produced benefits comparable to higher doses of the drug alone. The authors report this as the first demonstration of a positive interaction between a phage and a non-antibiotic drug.
Clinical Relevance
Phage therapy targets the microbial contribution to Crohn’s disease rather than the downstream inflammatory response, and the steroid-sparing signal is the most clinically interesting element: if it held up in people, it could allow lower corticosteroid doses and fewer of the associated harms.
That conditional is doing a lot of work, however. These are preclinical results, and results in experimental colitis models frequently fail to reproduce in human IBD. The team’s stated next steps are to test broader collections of bacterial strains from IBD patients and to develop phage combinations, which they describe as bringing the approach closer to human trials rather than at them. Clinicians should note that phage therapy for IBD remains experimental, is not available as a treatment option, and that no dosing, safety or efficacy data in patients yet exist.
Reference
Jackson K, Galipeau HJ, Hann A, et al. Phage intervention improves colitis and response to corticosteroids by attenuating virulence of Crohn’s disease-associated bacteria. Sci Transl Med. 2026;18(857):eadz4589. doi:10.1126/scitranslmed.adz4589
This article is a journalistic summary for informational purposes only. It does not constitute clinical advice or a recommendation to alter treatment decisions.