is a gram negative, microaerophilic, curved bacillus. It is motile, has flagellae and has a special affinity for human gastric mucosa.
Since its initial discovery it has been implicated in the pathogenesis of a number of gastroduodenal disorders including acute and chronic gastritis, gastric and duodenal ulceration, gastric cancer and gastric MALT lymphoma
Up to 50% of the population in developed countries such as Australia will have evidence of H. pylori infection by the age of 50 years. The organism is present in up to 92% of patients with active chronic gastritis, 88-100% with duodenal ulceration, 58-100% with gastric ulceration and 46-94% with gastric cancer. In duodenal ulcer disease eradication of the organism has been shown to markedly reduce ulcer recurrence rates and possibly change the natural history of the disease.
However, H. pylori is capable of causing a number of gastrointestinal disorders, including ulcers, and, much less commonly, stomach cancer. It is not clear why some people get these conditions and others do not.
In the United States and other developed countries, infection is unusual during childhood but becomes more common during adulthood. However, in developing countries, most children are infected with H. pylori before age 10.
RISK FACTORS — H. pylori is probably spread by consuming food or water contaminated with fecal matter. Children living in developing countries may become infected after swimming in contaminated pools, streams, or rivers, by drinking contaminated water, or by eating uncooked vegetables.
H. pylori causes changes to the stomach and duodenum (the first part of the small intestine, show figure 1 ). The bacteria invades the protective tissue that lines the stomach. This leads to the release of certain enzymes and toxins. These enzymes and toxins may directly or indirectly injure the cells of the stomach or duodenum.
As a result of these changes, the stomach and duodenum are more vulnerable to damage from digestive juices, such as stomach acid. This results in chronic inflammation in the walls of the stomach (gastritis) or duodenum (duodenitis).
SYMPTOMS — Most individuals with chronic gastritis or duodenitis have no symptoms. However, some people develop more serious problems, including stomach or duodenal ulcers. Ulcers can cause a variety of symptoms or no symptoms at all.
Common complaints include pain or discomfort (usually in the upper abdomen), bloating, feeling full after eating a small amount of food, lack of appetite, nausea, vomiting, and dark or tar-colored stools. Ulcers that bleed can cause a low blood count and fatigue.
Nevertheless, because so many people in the world are infected with H. pylori, it is considered to be an important cause of stomach cancer. People who live in countries in which infection occurs at an early age are at greatest risk of stomach cancer.
Breath tests — Breath tests (known as urea breath tests) require that the patient drink a specialized solution containing a substance (13C [carbon]- or 14C-labeled urea) that is broken down by the H. pylori bacterium. The breakdown products can be detected in a person's breath.
Endoscopy — Testing may include endoscopy of the upper gastrointestinal tract to confirm certain gastrointestinal conditions, such as peptic ulcer, as well as infection with H. pylori. However, endoscopy is not required for the diagnosis of H. pylori.
Although H. pylori infection is the most common cause of ulcers, not all patients with ulcers have H. pylori. Certain medications (eg, aspirin, ibuprofen (Motrin®, Advil®), naproxen (Aleve®)) can also cause peptic ulcers. Thus, testing for H. pylori is recommended.
However, it may be considered for selected people, such as those with a family history or concern about stomach cancer, particularly individuals of Chinese, Korean, or Japanese descent; these groups have a higher incidence of stomach cancer.
Nonulcer (functional) dyspepsia — Because H. pylori infection is so common, researchers have tried to determine if other illnesses could be caused or worsened by the infection. One example of this is a condition known as nonulcer (functional) dyspepsia
In general, studies suggest that few, if any, patients with functional dyspepsia benefit from treatment of H. pylori infection. Most patients with functional dyspepsia are tested for H. pylori before treatment is recommended.
The organism is usually present in the gastric antrum and lives beneath the mucus layer. One of its special characteristics is its ability to produce urease, an enzyme that is not normally found in the human stomach.
Tests for IgG antibodies are the most sensitive as once infected with the organism an IgG response is seen in 95%, an IgA response in 68-80% and IgM response in only 14% of infected patients. The majority of tests are performed on blood and the sensitivity of salivary antibody tests is low, probably as the majority of salivary antibodies are IgA rather than IgG. It is important that serological tests are locally validated.