On this page
For most of the twentieth century, a stomach ulcer was blamed on stress, spicy food and too much acid. Patients took antacids, the ulcers healed, and then they came back. Two doctors in Perth, Australia, showed that the main cause was a bacterium, and that a short course of antibiotics could cure the disease. This post covers what they saw, the numbers in their landmark paper, and the self-experiment that made the story famous.
Who were Warren and Marshall?
The Nobel facts pages give the basics. J. Robin Warren was born on 11 June 1937 in Adelaide and died on 23 July 2024 in Perth. Barry Marshall was born on 30 September 1951 in Kalgoorlie, Western Australia. They shared the 2005 Nobel Prize in Physiology or Medicine "for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease".
Warren was a pathologist at Royal Perth Hospital. In his Nobel biography he writes that in 1979, on his 42nd birthday, he noticed bacteria growing on the surface of a gastric biopsy. Over the next two years he collected many examples and saw that they went with chronic gastritis, inflammation of the stomach lining. Marshall, a young doctor in training, joined him in 1981 to follow up the patients.
What did their 1984 paper show?
The 2005 Nobel press release says Warren had seen the curved bacteria in about 50% of patients whose stomachs were biopsied, always with inflammation nearby. Marshall and Warren then studied biopsies from 100 patients. After several failed attempts, Marshall grew the bacterium in culture.
Their paper in The Lancet in 1984 reports the results. Biopsies were taken from 100 consecutive patients having a gastroscopy. Spiral or curved bacilli were seen in 58. Bacteria cultured from 11 of those were gram-negative, had flagella and grew only with little oxygen; they looked like a new species. The bacteria "were present in almost all patients with active chronic gastritis, duodenal ulcer, or gastric ulcer".
Worked example: reading the numbers
Bacteria seen: 58 of 100 patients = 58%.
Successfully cultured: 11 of 58 = 0.19, or about 19%. Growing this organism was hard, which is why culture lagged far behind what the microscope showed.
From infection to ulcer: the press release says *H. pylori* lives in the stomachs of about 50% of all humans, and about 10 to 15% of infected people will at some time have a peptic ulcer. In a town of 1,000 people that means about 500 infected, and 0.10 × 500 = 50 to 0.15 × 500 = 75 who develop an ulcer.
So most infected people never get an ulcer. That is one reason the link was easy to miss: the bacterium is common, the disease is not.
Why did Marshall swallow the bacteria?
The idea met strong resistance. In his Nobel biography, Marshall calls 1984 "a difficult year": papers were rejected and he could not infect an animal model. So he decided to use himself. He writes that he did not discuss it with the hospital ethics committee, or in detail with his wife.
The result was published in the Medical Journal of Australia in 1985 under the title "Attempt to fulfil Koch's postulates". A volunteer with a normal stomach lining swallowed the bacterium, became mildly ill for 14 days, and had gastritis confirmed on the tenth day. Koch's postulates are the classic rules for linking a microbe to a disease; our post on Robert Koch's postulates explains them.
Self-experiments like this would not be allowed today without ethical review, and you should never copy one. The point is the logic: to show cause, you need to see the disease follow the infection.
How did the treatment change?
The press release explains that ulcers healed with acid-blocking drugs but often relapsed, because the bacteria and the inflammation stayed. Patients were cured only when the bacteria were eradicated. Today *H. pylori* is known to cause more than 90% of duodenal ulcers and up to 80% of gastric ulcers, and the disease can be cured by a short regimen of antibiotics and acid secretion inhibitors.
One of those acid inhibitors has its own story: the drug cimetidine came from James Black's work on receptor-blocking drugs.
What can a student take from their way of working?
Look at what is on the slide. Warren saw bacteria that others had treated as unimportant.
Pair different skills. A pathologist's eye and a clinician's access to patients made the study possible.
Design the test that settles it. Showing infection before disease was the step that changed minds.
If cause, correlation and Koch's postulates feel slippery, the Fermi Concept Library covers every concept in biology, each with its own lesson and its place in the map.
Try it now: list the four steps of Koch's postulates and mark which one Marshall's self-experiment tested.
