Could a friendly virus help treat inflammatory bowel disease?
Crohn’s disease is an inflammatory bowel disease linked to an imbalance in the gut microbiome. Now, researchers at McMaster University have found in mice a way to target and ‘turn off’ only the bad gut bacteria using specially trained, precision viruses. This breakthrough paves the way for treatments tailored to each patient
Westernization has been linked to an increasing number of people affected by inflammatory bowel disease (IBD), particularly children. North America faces one of the highest rates of IBD in the world. Although current treatments can be effective, they may fail over the long term or require escalating doses, increasing the risk of side effects
IBD is shaped by a combination of genetics, immune responses and the gut microbiome. Some people with Crohn’s disease often carry high levels of a particular bacterium called adherent-invasive Escherichia coli (AIEC), which burrows into the gut lining and fuels inflammation. While antibiotics can push the infection back, they act like a blunt instrument – wiping out the good bacteria right along with the bad, which can ultimately make the problem worse
McMaster researchers have developed in mice a precise way to treat IBD using bacteriophages, which are ‘smart’ viruses that target specific harmful bacteria without harming beneficial bacteria
The research team focused on AIEC strains isolated from patients with Crohn’s disease, which are harmful bacteria difficult to identify and target. “One challenge is that AIEC are defined by what they do, not simply by how they appear in a microbiome analysis,” says Elena Verdu, professor in the Department of Medicine and director of the Farncombe Family Digestive Health Research Institute. “To identify them, we need to test their behavior, such as their ability to adhere to and invade intestinal cells and persist in immune cells.”
Instead of eliminating harmful AIEC, the bacteriophage, or phage, flipped a genetic switch controlling the bacteria’s ability to invade the gut wall, disarming it rather than destroying it. “Phages work like a lock-and-key system – each phage targets only certain bacteria. That precision gives us a way to intervene without wiping out the entire microbiome,” explains Zeinab Hosseinidoust, associate professor in the Department of Chemical Engineering and the School of Biomedical Engineering.
As a result, the mice developed less severe colitis and fewer flare-ups. The researchers also found that phage therapy enhanced the effectiveness of a common steroid used to calm inflammation (budesonide).When combined with the phage, a lower-than-standard dose of the steroid produced benefits comparable to those of higher doses of the drug alone. Many drugs for IBD lose effectiveness over time because they do not address the underlying cause driving inflammation at the microbial level. These findings provide early evidence that editing bacterial behavior, not just killing bacteria, could become a feasible complementary strategy.
The findings point to a precision‑medicine approach for IBD. The bacterial function targeted by the phage can be measured in stool samples and was found to be higher in a subset of patients with Crohn’s disease, suggesting a potential way to identify those who could benefit most from this therapy. Next steps for the team include evaluating broader collections of bacterial strains from IBD patients and developing combinations of phages – work that brings the approach closer to human trials.
“If we can identify which patients carry the harmful bacterial function, we could, in the future, intervene with a targeted therapy designed specifically to turn down that activity,” says Verdu
Note: This article has been edited for clarity and length based on the original press release
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
July 27th, 2026
By Andreu Prados
Categories: Gut Microbiota, Gut Microbiota Composition, Inflammation, News Watch
Tagged: Gut health, Gut microbiome, IBD, Inflammation, Inflammatory bowel disease, Phages
Andreu Prados
Andreu Prados is a science and medical writer specializing in making trusted evidence of gut microbiome-related treatments understandable, engaging and ready for use for a range of audiences. He holds bachelor’s degrees in Pharmacy and Human Nutrition and Dietetics and a PhD in nutrition communication. Follow Andreu on Twitter @andreuprados
