What is helicobacter pylori?

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 for developing cancer.

Exposure routes: Ingestion of contaminated food and water.
Transmitted person to person by oral-oral and oral-fecal routes. Maternal
infection associated with increased risk of infection in children.

Where found: Distribution of the organism is worldwide. There is a higher incidence in developing countries and where overcrowded and unsanitary conditions exist.

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 is 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 a H. pylori infection.

Not all H. pylori infections will lead to cancer.

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
pathologist J. Robin Warren with 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 associated with reduced risk of gastric cancer and
reduced progression of gastric precancerous legions.

Ford, Alexander C., et al.
"Helicobacter pylori Eradication Therapy to Prevent
Gastric Cancer in Healthy Asymptomatic Infected Individuals: Systematic
Review and Meta-Analysis of Randomised Controlled Trial."
BMJ 348 (2014): G3174. Web. 17 Oct. 2014.

Khan, Abdul Arif, ed. Bacteria and
Cancer. Dordrecht: Springer, 2012. Print.

Manfredi, Marco, and Gian Luigi
de'Angelis, eds. Helicobacter pylori: Detection Methods, Diseases
and Health Implications. New York: Nova Biomedical, 2013.
Print.

Moss, Steven F. Gastric
Cancer. London: Elsevier, 2013. Print.

Wong, B. C., et al. "Effects of Selective
COX-2 Inhibitor and Helicobacter pylori Eradication on
Precancerous Gastric Lesions." Gut 61.6 (2012): 812–18.
Print.