The intestinal flora is a group of bacteria designated to be planted in the human intestine and interdependent with the human body for a long time, including more than 40 genera, 400 to 500 species, and 100 trillion in number, which is 10 times more than the human body cells, and is equivalent to a human liver in weight, accounting for 1/3 to 2/5 of the daily fecal excretion of healthy adults. According to the distribution level and existence of intestinal flora in the intestine, it can be divided into Membrane flora and luminal flora: Membrane flora, also known as native bacteria, can colonize close to the mucosal surface a few days after birth, are long-term resident bacteria, and still maintain a high number in adulthood, and have close contact with the epithelium of the colonization site, such as Bifidobacterium, Lactobacillus anaerobicus, Bacillus mimicus, etc.; luminal flora, also known as foreign bacteria, mainly exist in the intestinal cavity, are small, unstable transit bacteria, such as Pseudomonas aeruginosa, Enterobacter Once the number of luminal flora increases, it can cause diseases. According to the relationship between intestinal flora and human body, we artificially divide them into three categories: 1. There are individual differences in the composition and number of intestinal flora of different people, which may be controlled by the hereditary nature of the individual.