Gut bacteria seek out stomach injuries.

The bacterium that causes ulcers and gastric cancer, Helicobacter pylori, can detect, home-in-on and invade weaknesses in the stomach wall within minutes, new research has shown. 

H. pylori is carried in the guts of about half the human population, many of them without symptoms. But, in some cases, coincidental damage to the stomach lining by drugs, smoking, certain foods or alcohol may open up a chink in our defenses allowing the bug to slip through, delay the healing process and trigger the formation of an ulcer. 

That was the hypothesis, but no one knew for sure how it happened, until now. Working with mice, University of Cincinnati scientist Marshall Montrose and his colleagues set up a system allowing them to watch the stomach lining with a microscope and introduce tiny lesions, affecting just a few cells, with a laser.

They could then introduce Helicobacter pylori bugs, which had been programmed to glow green to make them easy to see, and follow where they went. Incredibly, within just minutes of the injury being made, the glowing bugs congregated in high numbers at the injury site where they set up sites of infection that prevented the injury from healing. 

Control mice, with the same injury but no Helicobacter added, healed completely in about a week. In comparison, the H. pylori colonised animals still had stomach damage a month later. "We suspect that the breach in the stomach lining releases factors that attract the bugs - and they swim incredibly quickly to the site," says Montrose.

These factors might include salts, and nutrients, but could include the same inflammatory signals that the tissue releases to promote healing. The bugs sniff it out and follow the scent upstream. "This gives us the first living insights into how these bugs interact with injuries to provoke chronic damage to the stomach." 

The scientists hope that the new findings, published this week in PLoS Pathogens, will lead to the discovery of new drugs capable of disrupting the process and preventing the bugs gaining a toe-hold in the first place.