• 13C-urea breath test [ Time Frame: one month after finishing study drugs ] [ Designated as safety issue: No ]
• gastroscopy with biospy for microbiology and histology (alternate) [ Time Frame: one month after finishing test therapy ] [ Designated as safety issue: No ]

Helicobacter pylori is a bacteria that infects the lining of the stomach and is associated with ulcers. Helicobacter pylori may also increase the long-term risk of developing certain forms of gastric cancer. Curing this infection generally requires that patients take 2 or more antibiotic medications and a stomach acid suppressing medication for about two weeks. Current treatments do not always cure the infection and a new treatment is being tested in this study. The drugs involved in the new 4 drug treatment have been widely used for treatment of this infection. It remains unknown what is the best and most cost effective way to give them. This study will compare three different ways of using these drugs.

Subjects must have active Helicobacter pylori infection in order to participate in this study.

The purpose of this study is to compare different methods of giving combination drug therapy for treating Helicobacter pylori infection of the stomach. The entire study will last less than 2 years. Each subject will be participating in the study for approximately 60 days.

A total of 360 subjects will be asked to participate in this study.

Before participating in this study, subject's must have undergone to confirm the presence and to assess the susceptibility of Helicobacter pylori. Qualified subjects will receive 4 drugs which are to be taken as part of the study treatment: an acid suppressing drug (name), amoxicillin, clarithromycin and metronidazole. The doses are 1 grams of amoxicillin, 40 mg of esomeprazole (Nexium), 500 mg of metronidazole and 250 mg of clarithromycin. Each drug will be given twice a day to be taken twice a day with the morning and evening meals. Subjects will receive one of three different combinations. The choice of which will be randomly chosen by the use of a computer program. The regimes are: all 4 drugs daily for 5 days, all 4 drugs daily for 10 days, and two drugs (esomeprazole and amoxicillin) for 5 days then all for drugs for 5 additional days.

Subjects will be asked to return within 4 days after completion of the treatment to evaluate how they did with the drugs. They will be asked bring back all unused medication and the bottles or containers that the medicine was packaged in. Your medication use and tolerance to the study drugs will be assessed. The treatment portion of the study will be complete at this point.

Evaluation of the effect of the treatment will take place 4-6 weeks after the end of therapy. Subjects will come back to the study site and will have a UBT or repeat endoscopy, if clinically indicated to verify that the Helicobacter pylori has been cured. Subjects will be asked not to take antibiotics or any other drugs that may affect the outcome of the breath test used to confirm that the treatment was successful.

• Drug: sequential antibiotics (esoprazole, amoxicillin, esoprazole, clarithromycin, metronidazole)
• Drug: continuous antibiotics (esoprazole, amoxicillin, clarithromycin, metronidazole)

• Active Comparator: esoprazole and amoxicillin and clarithromycin and metronidazole for 10 days
• Experimental: esoprazole and amoxicillin for 5 days, followed by esoprazole and clarithromycin and metronidazole for 5 more days

Inclusion Criteria:

• Male or non-pregnant female aged 18 to 75 years inclusively.
• Mental and legal ability to give a written informed consent.
• Active H. pylori infection.

Exclusion Criteria:

• Previous surgery of the stomach such as partial gastrectomy.
• Use of antibiotics within the preceding 30 days.
• Regular use of bismuth compounds (>3 times per week) in the 30 days before enrollment.
• Presence of serious medical condition(s) precluding participation or endoscopy with biopsy.
• Use of concomitant medication(s) known to interact with study medication.
• Presence of Zollinger-Ellison Syndrome.
• Pregnancy or lactation.
• Allergy to any of the study medications.
• Contraindication(s) to the use of any of the study drugs.
• Participation in a clinical trial within the last 30 days.
• Unwillingness to abstain from alcoholic beverages.
• Patients taking other medications including warfarin, antipsychotics, or chronic NSAIDs will also be excluded. Aspirin at a dose not more than 325 mg/day will be permitted.