What is the name of the bacterium that causes peptic ulcers?

Helicobacter pylori is the bacterium associated with most infection-related peptic ulcers. This spiral-shaped, gram-negative organism colonizes the stomach’s protective mucus layer, where its flagella help it move through the lining and its urease enzyme helps it tolerate stomach acid. Persistent infection can cause gastritis and damage the defenses that protect the stomach and duodenum.

Australian physician Barry Marshall and pathologist Robin Warren identified the organism in patients in the early 1980s. Their findings challenged the widely held belief that ulcers were mainly caused by stress, spicy food, or excess acid. Marshall famously swallowed a culture of the bacterium and developed gastritis, helping demonstrate that it was a genuine pathogen rather than an incidental contaminant.

The bacterium was initially called Campylobacter pylori before being assigned to the Helicobacter genus in 1989. Marshall and Warren received the 2005 Nobel Prize in Physiology or Medicine. Not every ulcer is caused by H. pylori: long-term use of nonsteroidal anti-inflammatory drugs, such as aspirin, is another major cause.