• Primary end-point of the study is to compare the eradication rate of levofloxacin-based therapy (LALa regimen for 7 days) to that achieved with the standard first line regimen (CALa regimen for 7 days). [ Time Frame: One year ] [ Designated as safety issue: Yes ]
  

Determination of H. pylori status Prior to enrollment, the status of H. pylori infection will be determined by (1) rapid urease test (CLO test, Kimberly-Clark, USA) from antrum biopsy, (2) histological examination (Giemsa stain) of antral and body samples (two from the antral mucosa and two from the corpus mucosa), and (3) culture. Positive in any two of the three tests will be defined as positive for H. pylori infection. After-treatment H. pylori status will be determined by 13C-Urea Breath Test (13C-UBT) at 6 weeks after the completion of treatment. Successful eradication of H. pylori is defined as a negative 13C-UBT result.

Eradication Therapy Using a computer-generated number sequence, patients who meet the inclusion criteria and do not have any one of the exclusion criteria will be randomized to receive one of the following regimens: (1) CALa regimen: clarithromycin 500mg twice daily, amoxicillin 1000mg twice daily, and lansoprazole 30mg twice daily for 7 days, or (2) LALa regimen: levofloxacin 750mg (levofloxacin500 1.5 tablets) once daily, amoxicillin 1000mg twice daily, lansoprazole 30mg twice daily for 7 days (Figure 1). Adverse events will be recorded throughout the trial and during the follow-up period. Patients who do not return for 13C-UBT at 6 weeks after completion of treatment will be considered lost-to-follow-up and will be excluded from the per protocol (PP) analysis.

Rescue regimen for treatment failure after first-line regimen Patients who remained positive for H. pylori after the initial treatment as determined by the 13C-UBT will be followed by endoscopy. Biopsy will be done for H. pylori culture and antibiotic susceptibility test. All of them will then be treated with rescue regimen. The rescue regimens will be given in a cross-over manner (Figure 1). Patients who are treated with CALa regimen for 7 days as initial treatment will be treated with LALa regimen for 10 days as rescue treatment. Patients who are treated with LALa regimen for 7 days as initial treatment will be treated with CALa regimen for 10 days as rescue treatment.

Compliance and Adverse Effect Patients' compliance will be assessed by standardized interview at the end of treatment as well as by pill count in the medication boxes returned at the interview. Compliance is considered low when more than 20% of pills is found in the box. At enrollment, the patients will be informed of the common side effects from the studied antibiotics, including diarrhea, taste disturbance, nausea, bloating, loss of appetite, vomiting, abdominal pain, constipation, headache, and skin rash.