When Dr Barry Marshall swallowed Helicobacter pylori (H. pylori) bacteria to test the theory that they were responsible for stomach ulcers, some people branded him as crazy. But it was this daring move that led to one of the most significant medical discoveries of the past few decades: identifying H. pylori as a common bacterial infection affecting the stomach, and a major cause of ulcers. Until then, scientists had believed that bacteria were unable to survive in the stomach’s acidic environment.
The H. pylori bacterium (pictured) was discovered by Marshall and Dr Robin Warren, a pathologist, at Western Australia’s Royal Perth Hospital in 1983 after they spent several months attempting to grow the bugs in culture. They eventually succeeded only by accident when the culture was left for longer than usual over the Easter holidays.
However, despite managing to grow the bug and prove that it was a new organism, the medical world took some convincing. Finally, Dr Marshall swallowed a solution containing the bug to prove his point. Sure enough, vomiting and other symptoms of stomach inflammation appeared about a week later.
The discovery was a huge breakthrough for gastroenterology, revolutionising the treatment of stomach and duodenal ulcers (often called peptic ulcers).
Helicobacter pylori is a bacterium that survives in the stomach’s harsh acidic environment. H. pylori produces chemicals that damage the stomach’s protective mucous lining, allowing breaks to form, which are then vulnerable to erosion by the stomach acid and gastric juices.
H. pylori can be responsible for causing:
In fact, it is responsible for causing more than 90 per cent of duodenal ulcers and about 70 per cent of stomach ulcers.
Once someone contracts H. pylori, the infection generally persists for many years, possibly for life, unless they develop ulcer symptoms and are treated with antibiotics to kill the H. pylori.
Although anyone can potentially be infected with H. pylori, usually during childhood, the chance of becoming infected in Australia is much less than it once was.
It is thought that about 40 per cent of people in Australia aged over 40 are infected with the bacterium, with less than 10 per cent of children affected.
Men and women are equally affected by this germ, and infection rates are higher among older people and certain ethnic groups, such as Middle Eastern and Asian people.
However, many infected people do not develop ulcers or any other symptoms and are never aware that they carry the bug.
Scientists are unsure of the exact mechanism that allows people to become infected with the bacteria. H. pylori has been detected in the saliva of infected people, prompting scientists to think that it may be spread by mouth-to-mouth contact, such as kissing. Infection may also happen by sharing food or utensils with an infected person. It is also thought that infection occurs through contact with the stomach contents of an infected person, such as by coming into contact with their vomit. H. pylori can be spread easily among family members.
Because no one knows exactly how the bacteria are spread, preventing H. pylori infection is also difficult. Scientists are currently working on the development of a vaccine to prevent H. pylori infection.
Indigestion is the most common symptom of the bacteria, although most people experience no symptoms. Other symptoms include nausea, abdominal pain, bloating and burping.
H. pylori infection can be diagnosed using a breath test, a blood test or a biopsy test.
This test uses the fact that H. pylori contains the enzyme urease, which breaks down urea in the stomach to ammonia and carbon dioxide. In the test you swallow a special urea solution which is chemically ‘labelled’ so that it can be traced later. If you have H. pylori in your stomach it will break down the ‘labelled’ urea into ammonia and carbon dioxide. Because the carbon dioxide will be ‘labelled’ it can be detected in your breath for a short time.
Under normal circumstances, if you are infected with H. pylori your immune system will recognise that the bacterium is foreign to your body and will produce antibodies directed against it. The blood test for H. pylori detects this antibody and so it will show whether you have H. pylori present in your body or have had a recent infection with it. However, even if the test is positive it does not mean that you have an ulcer and you may not have any symptoms of the infection. Your doctor will be able to advise you if you should undergo further examination.
A biopsy is a tiny sample of tissue. This can be obtained from the stomach by carrying out a procedure called a gastroscopy. During a gastroscopy, a small flexible tube is passed through the mouth, down the gullet (oesophagus) and into the stomach, allowing a doctor to view the oesophagus, duodenum and stomach. A small piece of the stomach lining can be removed and then tested for the H. pylori bacteria. Gastroscopy is usually done under light sedation and should not cause more than minor discomfort.
A combination of medications is usually used to eradicate H. pylori. The most successful results are achieved with at least 3 different medications used at once. Treatment usually consists of a medication known as a proton-pump inhibitor (a potent stomach acid-lowering drug) in combination with 2 antibiotics or, less commonly, a bismuth drug combined with 2 antibiotics. Your doctor can prescribe combination packs, which contain all the medications you need for a course of treatment.
After you have been treated, you may be tested again by a breath test or gastroscopy, to check that the bacteria have been eradicated. Once the bugs have been eradicated, the risk of re-infection is low in Australia.
Last Reviewed: 11 March 2003