At present, triple therapy are recommended by various guidelines for the treatment of Helicobacter pylori (H. pylori) infection. Recent studies have shown worldwide high treatment failure rates with one week first line clarithromycin based triple therapy necessitating salvage strategy to eradicate H. pylori in primary treatment failure. However, the exact duration of bismuth based second line treatment is not determined. Therefore, the investigators performed this study to evaluate the eradication rate of 1 or 2-week quadruple regimen as a second-line therapy.

Inclusion Criteria:

• H. pylori infection
• Aged between 18-80 years
• Are willing to received eradication therapy for H. pylori

Exclusion Criteria:

• Children and teenagers aged less than 18 years or over 80 years
• Previous eradication therapy for H. pylori
• History of gastrectomy
• Previous allergic reaction to antibiotics
• Use of prompt pump inhibitors and antibiotics in the recent 4 weeks
• Active upper GI bleeding in the recent 1 week
• Contraindication to treatment drugs
• Pregnant or lactating women
• Severe concurrent disease or malignancy