Helicobacter pylori

by Courtney Humphries

Bacteria have long been known to dwell in the human digestive tract. But until a few decades ago, we assumed that no microbe could possibly make its home in the stomach, one of the most brutal territories in the human body. How could bacteria survive its churning seas of caustic acid?

But in the early 1980s, two Australian medical researchers, Robin Warren and Barry Marshall, began studying spiral-shaped bacteria isolated from the stomachs of patients with chronic gastritis (inflammation of the stomach lining) and ulcers. They became convinced that bacteria not only lived in the stomach but were causing disease. To prove it, Marshall took a step few scientists have dared:  he swallowed a drink swarming with the bacteria, infecting himself with these mysterious microbes. Shortly after, he developed acute gastritis.

The idea that stomach diseases could be caused by a bacterial infection wasn’t easily accepted. In the past, doctors thought ulcers were provoked by stress or some physical flaw in the patient. Modern medical research focused on the overproduction of stomach acid as the culprit. In the 1970s, powerful antacids called H2 receptor antagonists were developed to suppress acid secretion (now sold over the counter as Tagamet and Zantac), and were revolutionary in treating peptic ulcer disease. But there was a catch: patients often had to stay on the drugs indefinitely or their problems would recur. This was a boon to the drug industry, and in the mid-1980s Zantac became the best-selling drug in history.

Marshall’s little microbe, now called Helicobacter pylori, posed a threat: a course of antibiotics could cure what had been seen as a chronic disease. When a study in the New England Journal of Medicine showed that children with gastritis were infected with H. pylori, the news led to a drop in the stock price of Zantac’s maker, Glaxo.

We now know that some microbes are able to nestle into the lining of the stomach and live in relative safety there. Today, antibiotic therapy is widely prescribed around the world for H. pylori infection in the treatment of ulcers and gastritis. The microbe has since been linked to other stomach problems and to an increased risk of stomach cancer; recent research has suggested it might raise the risk of other diseases, including diabetes and Parkinson’s disease. Scientists are actively researching treatments for H. pylori infection as resistance to current antibiotics develops, including vaccines that could prevent infection in the first place.

But the story’s not over—research on H. pylori has challenged how we think about infections. At least half of the world’s population turns out to have this bug in the lining of their stomachs. Yet clearly they are not all diseased; it’s estimated that ten percent develop ulcers and one percent develop gastric cancer. And in fact, the presence of H. pylori has been associated with a decreased risk of some conditions.

Should everyone who carries H. pylori be treated with antibiotics, or just those with disease? This question has spurred intense debate. Some see H. pylori as a pathogen to be banished. Others see the microbe as one of our symbiotic bacteria that may have useful roles in the body; they worry that eradicating it could backfire, perhaps causing an increase in gastro-esophogeal reflux disease (GERD) and asthma.

We tend to view microbes in dualistic terms: They’re either with us or they’re against us. But reality has a way of challenging our assumptions. The story of this stomach-dwelling microbe has as many twists as its helical cell body.  Further research will help us learn more about it, and may also challenge our simplistic view of how we relate to microbes.

About the Author

Courtney Humphries is a freelance journalist and author in Boston, specializing in science, health, and nature. Her work has appeared in publications including the Boston Globe, Technology Review, Nature, Science, New Scientist, and Wired. She is the author of Superdove: How the Pigeon Took Manhattan….And the World, a natural history of pigeons published Smithsonian Books. She is a graduate of MIT’s Graduate Program in Science Writing.