The ancient Egyptians used to treat ulcers with bayberry--a plant that, less reassuringly, was also used to shrink hemorrhoids and to repel flies. In Merry Medieval England, the medication of choice was the poison hemlock. In 19th century Germany, a renegade doctor, Wilhelm Otto Leube, was so driven by the idea that ulcers could be cured by resting the bowel that he used to starve his patients for seven days. Several died.

    About a century ago, things began to change with the belief that stress and spicy foods were the cause, a perception that continues to this day with the promotion of bland foods for people with ulcers.

    The focus of treatment also made an enduring shift--to "antacid" tablets and powders to combat excess production of acid blamed for damaging the delicate gastic mucosa. Surgery became the norm for fixing the bleeding ulcers.

    This was the dogma that prevailed in the early 1980s, and it seemed unbreakable at the time. To challenge it, as the Nobel Committee said, required two men "with tenacity and a prepared mind."

    In 1982, Warren, an Australian pathologist who inspected gastric biopsies, noted that many of the samples of inflamed, ulcerated tissue under his microscope had curved rod-shaped bacteria.

    He asked Marshall, then a trainee in internal medicine, to investigate further, and by persistence and careful observation they isolated and grew the bacteria they saw, dubbed Helicobacter pylori.

    It was present in nearly all the patients they saw who had gastritis, or duodenal or gastric ulcers.

    Lacking the final proof that H. pylori was the cause of the problem, Marshall and another volunteer took the extreme step of swallowing cultures of the bacteria to test it. Both developed gastritis, although neither got an ulcer.

    But the momentum had started.

    Other scientists were able to confirm and amplify the duo's findings by culturing the bacteria from the stomachs of ulcer patients, and the link between H. pylori and ulcers was later established in many epidemiological studies.

    More than 90 percent of duodenal ulcers and up to 80 percent of gastric ulcers are linked to H. pylori, research has established.

    There are now several kinds of diagnostic tests for H. pylori, either by testing the blood for antibodies to the germ, by testing a sample retrieved by endoscopy or by a test that spots a tell-tale enzyme in the breath.

    Treatment, too, is swift and noninvasive, and the ulcer surgeon, whose intervention sometimes led to the death of the patient, has been sidelined.

    "Thanks to the pioneering discovery by Marshall and Warren, peptic ulcer disease is no longer a chronic, frequently disabling condition, but a disease that can be cured by a short regimen of antibiotics and acid secretion inhibitors," the Nobel Committee said.

    The groundbreaking work has in turn opened up new areas of research.

    One big zone of interest is understanding exactly how H. pylori is able to cause inflammation, and whether other chronic inflammatory conditions, such as Crohn's disease, may likewise be caused by a microbe.

    H. pylori is present in about 50 percent of all humans, and in poorer countries, where there is a greater risk of transmission through the oral-fecal route, almost the entire population may be infected. Despite this, only 10 to 15 percent of infected individuals go on to develop the disease, which points to genetic susceptibility among humans and genetic variation among H. pylori. Richard Ingham, AFP