Helicobacter pylori
Helicobacter pylori, commonly referred to as H. pylori, is a gram-negative, helical-shaped bacterium that can thrive in the acidic environment of the stomach. This unique bacterium has several flagella, enabling it to penetrate the protective mucus layer of the stomach. It is primarily transmitted through contaminated food and water, as well as through oral-oral and oral-fecal routes, with higher prevalence in developing countries characterized by overcrowded and unsanitary conditions. H. pylori infection has been linked to serious health conditions, including gastric cancer and B-cell gastric mucosa-associated lymphoid tissue (MALT) lymphoma, although not all infections lead to these outcomes.
Symptoms related to H. pylori infections can be nonspecific and may include heartburn, abdominal pain, and loss of appetite. Diagnosis typically requires a biopsy of the stomach lining. Over the years, significant advances have been made in the treatment of H. pylori infections, including the approval of new regimens by health authorities and the emergence of promising vaccine candidates. The discovery of H. pylori in the 1980s challenged long-held beliefs about bacteria's ability to survive in the stomach, ultimately reshaping our understanding of gastrointestinal health and disease.
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Subject Terms
Helicobacter pylori
ALSO KNOWN AS: Helico-bacter pylori, H. pylori, previously known as Campylobacter pylori, Campylobacter pyloridis
RELATED CANCERS: Gastric cancer (cancer of the stomach, adenocarcinoma), B-cell gastric mucosa-associated lymphoid tissue (MALT) lymphoma, pancreatic cancer
DEFINITION: Helicobacter pylori is a curved, helical-shaped gram-negative bacterium that produces urease, an enzyme that enables the organism to modify the stomach’s acid environment. It possesses four to six flagella that give the organism its motility, allowing it to penetrate the mucus gel layer of the stomach. Certain strains produce the cagA toxin, which has been associated with a higher risk of developing cancer.
Exposure routes: Ingestion of contaminated food and water. Transmitted person to person by oral-oral and oral-fecal routes. Maternal infection is associated with an increased risk of infection in children.
Where found: The organism is distributed worldwide. It is more prevalent in developing countries and areas with overcrowded and unsanitary conditions.
At risk: Elderly, children
Etiology and symptoms of associated cancers: Gastric cancer associated with H. pylori infection occurs in the antrum (lower) portion of the stomach and involves the inner lining of the stomach mucosa. Symptoms are nonspecific. Heartburn, bleeding into the stomach, loss of appetite, fatigue, and abdominal discomfort or pain are also associated with gastritis and peptic ulcer. A biopsy of the stomach is required for a definitive diagnosis.
H. pylori infection alters the gastric epithelial cells, triggering the body’s defense mechanisms. It is this response production of interleukin 6, tumor necrosis factor-alpha (TNF-alpha), and free radicals that may cause cancerous cells to develop, replicate, and spread. Stomach cancer can spread directly through the stomach wall to adjacent organs, or through the lymphatic system to the lymph nodes.
MALT is a rare form of non-Hodgkin lymphoma, a slow-growing cancer of the B-cell lymphocytes that develop in the stomach in response to an H. pylori infection.
Not all H. pylori infections will lead to cancer.
In the twenty-first century, advancements have been made in treating H. Pylori infections, reducing the risk of developing gastric cancers post-infection. In 2022, the US Food and Drug Administration approved vonoprazan-containing regimens to treat H. Pylori infection. In diagnosing H. Pylori infection, peptide mass fingerprinting emerged as a diagnostic tool that made identifying infections quicker and easier. Finally, vaccines against H. Pylori have shown promise in clinical trials.
History: For much of the twentieth century, it was thought that bacteria were unable to survive in the acid environment of the stomach. In 1981 pathologists J. Robin Warren and Barry J. Marshall isolated H. pylori from the human stomach mucosa and established a link between H. pylori and gastritis and peptic ulcers. Marshall proved their theory by infecting himself with the organism, developing gastritis, and recovering the organism from his stomach lining. In 1994 H. pylori was categorized as carcinogenic to humans (Group 1) by the World Health Organization’s International Agency for Research on Cancer (IARC). Treatment options for H. pylori infection include triple therapy for one to two weeks, which involves proton pump inhibitors such as esomeprazole, clarithromycin, and an antibiotic such as amoxicillin or an antimicrobial such as metronidazole. Eradication of H. pylori infection is associated with reduced risk of gastric cancer and reduced progression of gastric precancerous legions.
Bibliography
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