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A bacterial toxin disarms gut defenses against inflammation

Sonia Modilevsky1, Shai Bel1

  • 1Azrieli Faculty of Medicine, Bar-Ilan University, Safed, Israel.

Science (New York, N.Y.)
|November 20, 2025
PubMed

Insights

Bacteria found in patients with ulcerative colitis (UC) are toxic to macrophages and exacerbate gut inflammation in mouse models. This suggests a direct role for these specific bacteria in driving UC pathogenesis.

Area of Science:

  • Microbiology
  • Immunology
  • Gastroenterology

Background:

  • Ulcerative colitis (UC) is a chronic inflammatory bowel disease.
  • The gut microbiome plays a crucial role in UC pathogenesis.
  • Certain bacterial species may possess specific virulence factors contributing to inflammation.

Purpose of the Study:

  • To investigate the impact of bacteria isolated from UC patients on gut inflammation.
  • To determine if these bacteria exhibit macrophage-toxic properties.
  • To assess the role of macrophage-toxic bacteria in a mouse model of gut inflammation.

Main Methods:

  • Isolation and characterization of bacteria from ulcerative colitis patient samples.
  • In vitro assessment of bacterial cytotoxicity against murine macrophages.
  • Administration of identified macrophage-toxic bacteria to mice to induce or worsen gut inflammation.
  • Histological and molecular analysis of colonic tissue.

Main Results:

  • Bacteria isolated from UC patients demonstrated significant toxicity towards macrophages in vitro.
  • Oral administration of these macrophage-toxic bacteria led to increased gut inflammation in mice.
  • Inflammatory markers and tissue damage were significantly elevated in mice exposed to the bacteria.

Conclusions:

  • Macrophage-toxic bacteria present in the gut of ulcerative colitis patients can directly worsen gut inflammation.
  • These findings highlight a potential mechanism by which specific gut microbes contribute to UC.
  • Targeting these specific bacterial populations may offer a therapeutic strategy for ulcerative colitis.

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