Q. I read that the 2005 Nobel Prize for medicine went to 2 doctors who discovered that most stomach ulcers are caused by a bacterium. How did they figure that out?

A. It’s an interesting story. In the 1980s, when Dr. Barry Marshall and Dr. Robin Warren, both Australian, first proposed that a bacterium was responsible for ulcers, they were contradicting mainstream medical thinking. At that time, it was generally agreed that psychological stress was the main culprit behind ulcers. But when Dr. Warren studied tissue samples from people with ulcers, he consistently saw signs of inflammation near where he found the bacterium. Dr. Marshall was able to grow this bacterium, which turned out to be Helicobacter pylori—H. pylori for short. But their colleagues were still not convinced, so Dr. Marshall decided to use himself as a guinea pig. First he swallowed a gastroscopic tube so that another doctor could examine his stomach and take tissue samples. The exam confirmed that neither H. pylori nor inflammation was present. Ten days later, Dr. Marshall swallowed H. pylori. Soon he felt ill, and later tissue studies showed that he had developed stomach inflammation—clearly attributable to the introduction of the bacterium. The team’s discovery led to the use of antibiotics to treat ulcers. It also prompted other scientists to seek bacterial causes for diseases such as ulcerative colitis and coronary artery disease.

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