To test the efficacy of 14 day levofloxacin and bismuth-containing second-line therapy for resistant Helicobacter pylori infection, to compare with the classical quadruple therapy.

Inclusion Criteria:

• all patients had failed H.pylori therapies including clarithromycin, metronidazole and/or amoxicillin (if not allergic) before.

Exclusion Criteria:

• patients less than 18 years old,
• previous gastric surgery,
• pregnancy,
• lactation,
• major systemic diseases,
• administration of antibiotics,
• bismuth,
• antisecretory drugs in the preceding 8 weeks, or
• allergy to any one of the medication used in the quadruple regimens.