Helicobater pylori plays an important role in the development of gastric cancer. Eradication therapy can reducing the morbidity of gastric cancer, but can't totally prevent it especially when atrophy and more serious precancerous lesions already happened. Prior studies found the gastric bacterial difference among gastritis, intestinal metaplasia and gastric cancer. However, they didn't reach an agreement. Correa's model is widely accepted in the development of gastric cancer. The pathological change makes a more suitable environment for bacteria to overgrowth. This study are designed to analyze the gastric microbial difference of non-atrophic gastritis, atrophic gastritis, intestinal metaplasia, intraepithelial neoplasia and gastric cancer.

Inclusion Criteria:

1. Patients go through a gastric endoscopy examination with non-atrophic gastritis, atrophic gastris, intestinal metaplasia, intraepithelial neoplasia and gastric cancer.
2. Did not take any antibiotics,PPI,probiotics and chinese herbs in the past one month,and took less than one week in the past three months before the gastroscopy examination.
3. Sign the informed consent.

Exclusion Criteria:

1. Had been taken Helicobacter pylori eradication therapy before.
2. Previous gastrointestinal surgery.
3. During the pregnancy and lactation period.
4. With any serious diseases like liver failure,heart failure,renal failure,malignant tumor,alcoholism or any other disease that may effect the result.
5. With any mental problems.

patients go through a gastric endoscopy examination with non-atrophic gastritis, atrophic gastris, intestinal metaplasia, intraepithelial neoplasia and gastric cancer.