Heliobacteriosis Health Article

Definition

Helicobacteriosis refers to infection of the gastrointestinal tract with the bacteria, Helicobacter pylori (H. pylori). While there are other rarer strains of Helicobacter species that can infect humans, only H. pylori has been convincingly shown to be a cause of disease in humans. The organism was first documented to cause injury to the stomach in 1983, by two researchers in Australia, who ingested the organism to prove their theory. Since then, H. pylori has been shown to be the main cause of ulcer disease, and has revolutionized the treatment of peptic ulcer disease. It is also believed to be linked to various cancers of the stomach.

Description

H. pylori is a gram-negative, spiral-shaped organism, that contains flagella (tail-like structures) and other properties. In addition to flagella, which help the organism to move around in the liquid mucous layer of the stomach, H. pylori also produces an enzyme called urease, that protects it from gastric acid present in the stomach. As the production of this enzyme is relatively unusual, new diagnostic tests have enabled rapid identification of the bacteria.

H. pylori also produces two other chemicals: a cytotoxin called vacA, and a protein known as cagA. Patients with ulcer disease are more likely to produce the cytotoxin (vacA). The cagA protein not only occurs frequently in ulcer disease but also in cancer. It is still not known how these substances enable H. pylori to cause disease.

Causes and symptoms

Infection with H. pylori is largely dependent on two factors; age and income status. The bacteria is acquired mainly in childhood, especially in areas of poor hygiene or overcrowding. H. pylori is two to three times more prevalent in developing, non-industrialized countries. In the United States for example, the organism is believed to be present in about one third of the population.

The exact way in which H. pylori gets passed from one individual to another is uncertain, but person to person transmission is most likely. In most cases, children are felt to be the source of spread. Reinfection of those who have been cured has been documented, especially in areas of overcrowding.

The bacteria is well adapted to survival within the stomach. Not only does it survive there for years, but once infection begins, a form of chronic inflammation (chronic gastritis) always develops. In most individuals, initial infection causes little or no symptoms; however, some individuals such as the original researchers who ingested the bacteria, wind up with abdominal pain and nausea.

In about 15% of infected persons, ulcer disease develops either in the stomach or duodenum. Why some develop ulcer disease and others do not, remains unclear. Ulcer symptoms are characterized by upper abdominal pain that is typically of a burning or "gnawing" type, and usually is rapidly relieved by antacids or food.

Acid secretion increases in most patients with duodenal ulcers. This increase returns to normal once H. pylori is eliminated. It is now known that elimination of the bacteria will substantially decrease the risk of recurrent bouts of ulcer disease in the vast majority (85% or so) of patients.

In the last decade it has been shown that H. pylori is not only the prime cause of ulcer disease of the stomach and duodenum, but is also strongly associated with various tumors of the stomach. Bacterial infection is nine times more common in patients with cancer of the stomach, and seven times more common in those with lymphoma of the stomach (tumor of the lymphatic tissue), called a MALT tumor. It is believed that the prolonged inflammation leads to changes in cell growth and tumors. Eliminating H. pylori can lead to regression of some tumors.

In addition to the above damage caused by H. pylori, some individuals lose normal gastric function, such as the ability to absorb vitamin B₁₂.