Helicobacter pylori infection overview
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Differentiating Helicobacter pylori infection from other Diseases |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]
Overview
Helicobacter pylori infection is caused by H. pylori which is a gram-negative, microaerophilic, and acidophilic bacterium that infects various areas of the stomach and duodenum. It is the most prevalent, worldwide and chronic infection. It is associated with many gastro intestinal diseases like gastritis, peptic ulcer disease, adenocarcinoma and MALT lymphoma. It is estimated that 30%-40% of the United States population is associated with H. pylori infection.
Historical Perspective
The association between helicobacter pylori and peptic ulcers was made by Barry Marshall and Robin Warren in the year 1984 for which they were awarded Nobel prize in 2005 in physiology or medicine.
Pathophysiology
Person to person transmission is considered to be the most likely route of transmission of Helicobacter pylori. H. pylori is a noninvasive organism. It is found over mucus secreting cells but not in deeper gastric glands. Hence it can only inhabit gastric-type mucus but cannot colonize the esophagus or duodenum. Pathogenesis of H. pylori infection depends on bacterial, host and environmental factors.
Gastritis
The H. pylori induced gastritis includes the following stages. They are acute gastritis, active chronic gastritis, atrophy and intestinal metaplasia.
Peptic ulcer disease
H. pylori is closely associated with both duodenal and gastric ulcers. The estimated lifetime risk for the development of peptic ulcer disease is 10-20%, in patients with H. pylori infection. H. pylori causes up to 90% of duodenal ulcers and 60-80% of gastric ulcers.
Gastric adenocarcinoma
Gastric cancer is the second leading cause of cancer-related deaths worldwide and H. pylori is the strongest known risk factor for gastric cancer. H. pylori is considered as type I carcinogen. Among infected individuals, 1 to 3% develop gastric adenocarcinoma.
MALT lymphoma
MALT lymphoma (MALToma) is a form of lymphoma involving the mucosa-associated lymphoid tissue (MALT), frequently of the stomach, but virtually any mucosal site can be afflicted. It is a cancer originating from B cells in the marginal zone of the MALT. The evolution of gastric MALT lymphoma is a multistage process starting with the infection of H. pylori resulting in the recruitment of B-cell and T-cells and other inflammatory cells to the gastric mucosa.
Causes
Helicobacter pylori is a gram-negative, microaerophilic, and acidophilic bacterium that infects various areas of the stomach and duodenum. Many cases of peptic ulcers, gastritis, duodenitis, and perhaps some cancers are caused by H. pylori infections. However, many who are infected do not show any symptoms of disease. Helicobacter spp. are the only known microorganisms that can thrive in the highly acidic environment of the stomach. H. pylori's helical shape (from which the genus name is derived) is thought to have evolved to penetrate and favor its motility in the mucus gel layer.
Differential Diagnosis
Helicobacter pylori infection must be differentiated from other diseases that cause nausea, vomiting, abdominal pain, epigastric pain and unexplained weight loss such as atrophic gastritis, GERD, gastrinoma, peptic ulcer disease, gastric adenocarcinoma, stress-induced gastritis and non-Hodgkin's lymphoma.
Epidemiology and Demographics
H. pylori inhabits more than 50% of world's population, especially in developing countries. The prevalence of infection increases with age. The prevalence of H. pylori is higher in developing countries than that in developed countries. In the United States, H. pylori infection is a common disease that tends to affect African Americans, Hispanics, and the elderly compared to whites.
Risk Factors
Common risk factors in the development of H.pylori infection are contaminated food and water, poor hygiene, over crowding, lower socio-economic status, smoking, age and race.
Screening
According to the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for H.pylori infection.
Treatment
Medical Therapy
Persons with active gastric or duodenal ulcers or documented history of ulcers should be tested for H. pylori, and if found to be infected, they should be treated. To date, there has been no conclusive evidence that treatment of H. pylori infection in patients with non-ulcer dyspepsia is warranted. Testing for and treatment of H. pylori infection are recommended following resection of early gastric cancer and for low-grade gastric MALT lymphoma. Retesting after treatment may be prudent for patients with bleeding or otherwise complicated peptic ulcer disease. Treatment recommendations for children have not been formulated. Pediatric patients who require extensive diagnostic work-ups for abdominal symptoms should be evaluated by a specialist.
Primary Prevention
Since the source of H. pylori is not yet known, recommendations for avoiding infection have not been made. In general, it is always wise for persons to wash hands thoroughly, to eat food that has been properly prepared, and to drink water from a safe, clean source.