Helicobacter pylori (H. pylori) is the bacteria responsible for most ulcers and many cases of stomach inflammation (chronic gastritis).

The bacteria can weaken the protective coating of the stomach, allowing digestive juices to irritate the sensitive stomach lining.

As many as half of the world's population is infected with H. pylori. Those living in developing countries or crowded, unsanitary conditions are most likely to contract the bacterium, which is passed from person to person. H. pylori only grows in the stomach, and is usually contracted during childhood.

Interestingly, many people have this organism in their stomach, but don't get an ulcer or gastritis. It seems that other factors must also be present for the damage to take place. The factors that increase your risk for an ulcer from H. pylori include:

• Abnormal immune response in your stomach
• Certain lifestyle habits, like coffee drinking, smoking, and alcohol consumption

If you are a carrier of H. pylori, you may have no symptoms. If you have an ulcer or gastritis, you may have some of the following symptoms:

• Abdominal pain
• Belching and regurgitation
• Bloating and fullness
• Dyspepsia or indigestion
• Feeling very hungry 1 to 3 hours after eating
• Mild nausea (may be relieved by vomiting)

Simple blood, breath, and stool tests can determine if you are infected with H. pylori. If you have symptoms, your doctor will determine if you are an appropriate candidate for these screening tests.

The most accurate way to diagnose H. pylori, however, is through upper endoscopy of the esophagus, stomach, and duodenum. Because this procedure is invasive, it is generally reserved for people suspected to have an ulcer, or at high risk for ulcers or other complications from H. pylori, such as having stomach cancer. Risk factors include being over 45 or having symptoms such as:

• Anemia
• Difficulty swallowing
• Gastrointestinal bleeding
• Unexplained weight loss

Following treatment, breath and stool tests can determine if you have been cured of the infection.

Patients who have H. pylori and also have an ulcer are most likely to benefit from being treated. Patients who only have heartburn or acid reflux and H. pylori are less likely to benefit from treatment. The treatment fails in up to 20 percent of patients.

Treatment must be taken for 10 to 14 days. Medications may include:

• Antibiotics, such as clarithromycin (Biaxin), amoxicillin, tetracycline, or metronidazole (Flagyl)
• Histamine H2 blockers, such as cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), nizatidine (Axid, Tazac), and sometimes bismuth subsalicylate (Pepto-Bismol)
• Proton-pump inhibitors, such as omeprazole (Prilosec), lansoprazole (Prevacid), or esomeprazole (Nexium)

Once the H. pylori bacteria are gone from your body, the chance of being infected again is very low.

H. pylori infection is linked to stomach cancer and ulcer disease.

Call your health care provider if you have blood in your stool, abdominal pain, ongoing indigestion or heartburn, or any of the other symptoms mentioned above.

Seek immediate medical help if you are vomiting blood.

A clean and germ-free environment may help decrease your risk of H. pylori infection.

Chey WD, Wong BC. American College of Gastroenterology guideline on the management of Helicobacter pylori infection. Am J Gastroenterol. Aug 2007;102(8):1808-25.

Ables AZ, Simon I, Melton ER. Update on Helicobacter pylori treatment. Am Fam Physician. 2007;75(3):351-358.