Helicobacter pylori (H. pylori)

Helicobacter pylori is a spiral-shaped bacterium that's now known to play a major role in the development of the majority of peptic ulcers. H. pylori is found in the mucus layer of the stomach and duodenum.

It's estimated that around 50% of the population in Britain is infected with H. pylori, though not all go on to develop peptic ulcers. The infection is usually life-long and thought to be passed on during childhood. There is much research taking place to try to determine why some people with H. pylori are prone to ulcers and others are not.

Studies now show that around 95% of people with duodenal ulcers are infected with H. pylori. Of those with stomach ulcers, between 70% and 80% are infected.

There are a number of theories as to how H. pylori contributes to ulcers:

• It may alter the acid/alkaline balance in the digestive tract, leading to damage to the structure of the protective mucus membrane in the stomach and duodenum.
• It may damage the stomach lining. It does this because the spiral shape of H. pylori, and the way the bacterium moves, allows it to penetrate the stomach lining.
• It may become attached to stomach cells, further weakening the lining's defences and producing sites of local inflammation.
• It may stimulate acid flow in the stomach.
• It may release toxins which damage the mucus lining of the stomach.

It's the effect of the weakening and damage to the stomach lining, as well as the inflammation, that may lead to peptic ulcers. And it's in these weakened areas of tissue that ulcers are more likely to occur.