Two Australian scientists have been awarded the Nobel prize for medicine for their discovery that stomach ulcers can be caused by a bacterial infection.
Stomach ulcers can be treated with antibiotics
Robin Warren and Barry Marshall showed the bacterium Helicobacter pylori plays a key role in the development of both stomach and intestinal ulcers.
Thanks to their work these ulcers are often no longer a long-term, frequently disabling problem.
They can now be cured with a short-term course of drugs and antibiotics.
In 1982, when H. pylori was discovered by Dr Marshall and Dr Warren, stress and lifestyle were considered the major causes of stomach and intestinal ulcers.
H. pylori is found in the stomach of about 50% of all humans
In developing countries almost everyone is infected
Infection is typically contracted in early childhood, and the bacteria may remain in the stomach for life
In most people there are no symptoms
However, it can trigger ulcers in 10-15% of those infected
It is now firmly established that the bacterium causes more than 90% of duodenal (intestinal) ulcers and up to 80% of gastric (stomach) ulcers.
Dr Warren, a pathologist from Perth, paved the way for the breakthrough when he discovered that small curved bacteria colonised the lower part of the stomach in about 50% of patients from which biopsies had been taken.
He also made the crucial observation that signs of inflammation were always present in the stomach lining close to where the bacteria were seen.
Dr Marshall became interested in the findings and together they initiated a study of biopsies from 100 patients.
After several attempts, Dr Marshall succeeded in cultivating a hitherto unknown bacterial species - H. pylori - from several of these biopsies.
Together they found that the organism was present in almost all patients with gastric inflammation, duodenal ulcer or gastric ulcer.
Even though stomach ulcers could be healed by inhibiting gastric acid production, they frequently relapsed, since bacteria and chronic inflammation of the stomach remained.
Dr Marshall and Dr Warren showed patients could only be properly cured when H. pylori was eradicated from the stomach.
Dr Marshall proved that H. pylori caused gastic inflammation by deliberately infecting himself with the bacterium.
The Nobel citation praises the doctors for their tenacity, and willingness to challenge prevailing dogmas.
"By using technologies generally available they made an irrefutable case that the bacterium H. pylori is causing disease.
"By culturing the bacteria they made them amenable to scientific study."
It is thought that H. pylori infection can trigger an ulcer by stimulating increased acid production in the stomach, leading to damage to the stomach or intestinal lining.
Lord May of Oxford, President of the Royal Society, said: "The work by Barry Marshall and Robin Warren produced one of the most radical and important changes in the last 50 years in the perception of a medical condition.
"Their results led to the recognition that gastric disorders are infectious diseases, and overturned the previous view that they were physiological illnesses."