Levofloxacin and Bismuth-containing Therapy Versus Quadruple Therapy as Second-line Treatment of Resistant Helicobacter Pylori Infection

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.