Study of Faecal Bacteria Detection in Early Screening and Diagnosis of GC

Inclusion Criteria:

* 1）Age between 40 and 75;
* 2）Subjects in GC group are pathologically diagnosed as gastric cancer prior to any treatment such as surgery, endoscopic resection, chemotherapy, radiotherapy, immunotherapy, traditional Chinese medicine therapy, etc. The results of their preoperative abdominal enhanced CT or PET-CT indicated no obvious bowel abnormalities (inflammation, polyps, ulcers, tumors, erosions, melanosis, etc.);
* 3\) Subjects in HC group are diagnosed with chronic gastritis by endoscopy and pathology. without ulcers, polyps, tumors, severe erosions or bile reflux, and no obvious abnormal findings (inflammation, polyps, ulcers, tumors, erosions, melanosis, etc.) by colonoscopy within half a year;
* 4\) Subjects are willing to cooperate with this research and provide stool/mucosa samples as required.

Exclusion Criteria:

* 1\) with severe systemic infection, nasopharyngeal/oral cavity inflammation (periodontitis, gingivitis, tonsillitis, etc.), respiratory tract infection, soft tissue or skin infection, abscess or endocarditis within 3 months prior to recruitment;
* 2）prior medication history of the following medicine within 3 months: nonsteroidal anti-inflammatory drugs (NSAIDs), immunosuppressor, antibiotics, probiotics, hormones or immune-suppressants at least 1 week;
* 3）prior medication history of proton-pump inhibitors or H2 receptor inhibitors for over 2 months within 1 year;
* 4\) with a history of H.pylori eradication therapy within 1 year;
* 5\) with severe constipation, diarrhea or defecation habits changes within 3 months;
* 6\) personal history of cancer, organ transplantation, parasites infection or other severe digestive system diseases (inflammatory bowel disease, liver cirrhosis, etc.);
* 7\) with uncontrolled digestive bleeding, obstruction, perforation and any trauma or surgery within 3 months;
* 8\) with uncontrolled chronic metabolic or endocrine disorders, e.g. hypertension, diabetes, hyperlipidemia, hyperuricemia, etc.
* 9\) on a vegetarian diet or with great changes of eating habits within 3 months;
* 10\) refusal of participate in this study.