The researchers collect H.pylori-positive patients who need rescue therapy from the outpatient clinic. The subjects were randomized to receive a dose and frequency of tetracycline 500mg tid or qid of bismuth quadruple eradication therapy. 6-8 weeks after treatment, the subjects will re-take the 13C-urea breath test. Calculate the eradication rates, adverse reaction rates and patient compliance of each group.

The researchers collect H.pylori-positive patients who need rescue therapy from the outpatient clinic. If the subject meets the selection criteria but not the exclusion criteria, and signs an informed consent form, the researchers randomized the subjects in groups: subjects received a dose and frequency of tetracycline 500mg tid or qid of bismuth quadruple eradication therapy. The medication of groups are as follows. 6-8 weeks after the eradication treatment, the subjects will review the 13C-urea breath test, and the researcher records the results.

After all subjects were tested, the eradication rates, adverse reaction rates and patient compliance of each group were calculated.

According to the dose and frequency of tetracycline, it is randomized into a tid treatment group and a qid treatment group. The two groups of bismuth quadruple regimens are the same, as follows:

Tid group: Amoxicillin 1000mg bid+ Tetracycline 500mg tid+ Bismuth + Esomeprazole 40mg bid Qid group: Amoxicillin 1000mg bid+ Tetracycline 500mg qid+ Bismuth + Esomeprazole 40mg bid

Inclusion Criteria:

1. Patients aged 18-70.
2. Patients with H.pylori infection (Positive for rapid urease test or 13C/14C-urea breath test).
3. Patients who have previous failed H. pylori eradication treatment, and ≤ 2 times.

Exclusion Criteria:

1. Patients with serious underlying diseases, such as liver insufficiency (Aspartate aminotransferase or alanine aminotransferase greater than 1.5 times the normal value), renal insufficiency (Cr≥2.0mg/dL or glomerular filtration rate <50 ml/min), immunosuppression, malignant tumors, Coronary heart disease or coronary artery stenosis ≥75%.
2. Patients who are pregnant or lactating or unwilling to take contraceptive measures during the trial.
3. Patients with active gastrointestinal bleeding.
4. Patients with a history of upper gastrointestinal surgery.
5. Patients allergic to treatment drugs.
6. Patients with medication history of bismuth agents, antibiotics, proton pump inhibitor and other drugs within 4 weeks
7. Patients with other behaviors that may increase the risk of illness, such as alcohol and drug abuse
8. Patients who are unwilling or incapable to provide informed consents