The experiment that proved bacteria caused disease

In 1981, an Australian pathologist, Robin Warren, noticed that biopsy slides from patients diagnosed with gastric ulcers sometimes contained curved-shaped bacteria and lots of white blood cells. He showed the slides to a young clinician doing his gastroenterology rotation, Barry Marshall (pictured, above).

They tried to grow the bacterium, which needed special conditions, but they eventually discovered how to cultivate it.

Read more about the history of disease:

• Epidemiology: the history of disease and epidemics (Part I, pre-20th Century)
• Epidemiology: the history of disease and epidemics (Part II, post-20th Century)
• Robert Koch: how he identified one of the 19th Century's biggest killers
• 10 key scientists in our understanding of disease
• A timeline of discoveries

Making a solution of it, Marshall became his own guinea pig and swallowed the solution. He had symptoms of acute gastric inflammation and when they examined his stomach with a gastroscope, they saw the telltale signs of early ulcer formation.

Convinced that this bacterium was implicated in the common disease of peptic ulcer, they tried to convince the scientific community.

Conventional wisdom had it that the stomach was so acidic that no bacteria could grow there and thus was sterile. But treatments with antibiotics and bismuth solutions produced excellent results and eventually the world believed.

They demonstrated that simple experiments, of the kind that 19th-Century scientists could have performed, can produce unexpected results. They won the 2005 Nobel Prize for their elegant research. Nature is full of surprises, sometimes uncovered by traditional methods.