The purpose of this clinical trial is to evaluate the clinical efficacy of Bifidobacterium quadruple live bacteria tablets (Si Lian Kang) on reducing the incidence rate of adverse reactions of Helicobacter pylori quadruple eradication therapy and its influence on gastrointestinal flora.

Bismuth agent quadruple therapy (including bismuth agent and proton pump inhibitor combined with two antibiotics) is the first-line strategy to eradicate Helicobacter pylori in China. However, it may cause a series of adverse reactions, such as nausea, diarrhea, abdominal pain, constipation, and abnormal taste, etc., which leads to a decrease in patient compliance, thereby affecting the treatment effect. Many studies have found that adding probiotics to traditional Helicobacter pylori eradication therapies increase eradication rates and reduce the side effects of the treatment. Bifidobacterium tetrad live bacteria tablet is a compound microecological preparation composed of bifidobacterium infantis, lactobacillus acidophilus, enterococcus faecalis and bacillus cereus. This study aims to observe the clinical efficacy of Bifidobacterium quadruple live bacteria tablets (Si Lian Kang) on reducing the incidence rate of adverse reactions in Helicobacter pylori quadruple eradication therapy and on the effects of gastrointestinal flora.

Inclusion Criteria:

1. Voluntarily signing the informed consent form;
2. Aged 18-65 years old(including 65), male or female;
3. Patients aged 35-65 years old(including 35) with positive Helicobacter pylori should undergo gastroscopy, and the gastroscopy report shows normal or chronic gastritis;
4. Patients aged 18-35 years (including 18) with positive Helicobacter pylori are not required to perform gastroscopy examination if there is no obvious clinical symptoms, or applying report of gastroscopy within 6 months showing normal or chronic gastritis.

Exclusion Criteria:

1. Gastroscopy report or previous medical history showed significant esophagus-gastric diseases, including gastric cancer, peptic ulcer, oesophagitis and esophageal erosion;
2. Patients with chronic diarrhea and chronic functional constipation;
3. Other systemic diseases, including cardiovascular diseases, lung diseases, liver diseases (transaminase index is more than 2 times higher than the normal value), kidney diseases (creatinine index is higher than the normal value) and other important organs with severe lesions, severe metabolic diseases (diabetes, thyroid diseases), malignant tumors, and severe immune system diseases;
4. Abnormal stool routine results: fecal occult blood (+) or white blood cells (+);
5. Patients with severe psychological or mental diseases;
6. Those with a history of drug abuse or alcohol abuse;
7. Those who are allergic to the drugs in this study;
8. Those who have received Helicobacter pylori eradication therapy;
9. Drugs which affect the intestinal flora(including antibacterial drugs, microecological preparations, intestinal mucosal protectors, Chinese patent medicines, etc.) have been used in the past 1 month or need to be used continuously for more than 1 week in the experiment.
10. Pregnant or lactating women;
11. Participating or after completing other clinical trials Less than 3 months;
12. Others who researchers consider unsuitable for inclusion.