Personalized therapies for Crohn's and ulcerative colitis may follow from method that identifies harmful gut bacteria

by University Hospital Tübingen

edited by Gaby Clark, reviewed by Andrew Zinin

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Which gut bacteria contribute to the development or worsening of chronic inflammation? An international research team led by Dr. Lukas Mager from University Hospital Tübingen and Prof. Kathy McCoy from the University of Calgary has developed an approach to identify and selectively target such bacteria. The researchers identified two bacterial species that promote intestinal inflammation and compounds that selectively inhibit their growth. Published in the journal Gut, the study could pave the way for personalized therapies for inflammatory bowel diseases (IBD) such as Crohn's disease and ulcerative colitis.

In people with inflammatory bowel disease, the composition of the gut microbiome—the community of microorganisms living in the intestine—is often altered. However, it is frequently unclear which bacteria actually contribute to inflammation. The microbiome varies considerably from person to person, making it difficult to determine whether certain bacteria cause inflammation or simply become more abundant as a result of the disease.

Identifying disease-promoting gut bacteria

Together with researchers at the University of Calgary, Dr. Mager's team developed a method to identify disease-promoting bacteria in individual patients. To do so, the researchers compared stool samples collected from patients before and after treatment with antibiotics or fecal microbiota transplantation. The gut microorganisms from these samples were transferred into germ-free mice to investigate their effects on inflammation. The team then used antibodies produced by the immune system to isolate potentially harmful bacteria and assess their effects.

Two bacterial species promote inflammation

The researchers identified two bacterial species capable of triggering or exacerbating intestinal inflammation in susceptible hosts: Sarcina perfringens and Hathewaya massiliensis. Both activate cells of the innate immune system, thereby promoting inflammatory responses.

Additional analyses of international patient data sets showed elevated levels of Sarcina perfringens in approximately 25% to 30% of people with IBD, while Hathewaya massiliensis was found at elevated levels in around 5%. Experiments using intestinal organoids—miniature tissue models grown from human cells—provided further evidence that the bacteria promote inflammation through immune responses and can impair the function of intestinal epithelial cells.

"Inflammatory bowel disease does not have the same triggers in every patient. Our findings show that we can specifically identify bacteria that contribute to inflammation in individual patients. This is an important step toward more personalized treatment," explains Mager.

Targeted inhibition instead of broad-spectrum antibiotics

The research team then screened 1,518 previously approved compounds. They identified five substances capable of selectively inhibiting the growth of the two bacterial species without substantially affecting other common gut bacteria.

The antibiotic compound oxolinic acid proved particularly promising. In a mouse model, the compound reduced intestinal inflammation promoted by Sarcina perfringens with an efficacy comparable to that of the broad-spectrum antibiotic metronidazole. Unlike metronidazole, however, oxolinic acid had only a minor impact on the remaining bacterial community examined. This suggests that it may eventually be possible to selectively inhibit disease-promoting bacteria while largely preserving beneficial members of the gut microbiota.

Toward personalized therapies

Current treatments for inflammatory bowel disease primarily focus on controlling inflammatory responses. The new approach could complement these therapies by directly targeting specific bacterial triggers of inflammation.

Further research is needed before the approach can be used in clinical practice. In particular, researchers must establish whether selectively targeting these bacteria is also safe and effective in humans.

Publication details

Mahana Sabachvili et al., Identification and selective inhibition of patient-specific pathobionts in inflammatory bowel disease, Gut (2026). DOI: 10.1136/gutjnl-2026-339262

Journal information: Gut

Key medical concepts

Inflammatory Bowel DiseasesIntestinal inflammation

Clinical categories

GastroenterologyCommon illnesses & Prevention Provided by University Hospital Tübingen Who's behind this story?

Gaby Clark

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Citation: Personalized therapies for Crohn's and ulcerative colitis may follow from method that identifies harmful gut bacteria (2026, November 13) retrieved 13 November 2026 from https://medicalxpress.com/news/2026-11-personalized-therapies-crohn-ulcerative-colitis.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.