(1) pathogenic Escherichia coli, mainly including four types. In addition to enterotoxigenic Escherichia coli due to the production of heat-resistant or heat-resistant enterotoxin, causing cholera-like watery diarrhea, other pathogenic Escherichia coli can invade the intestinal mucosal epithelial cells and produce Shiga-like toxin growth, causing dysentery-like bloody diarrhea.

(2) Typhoid fever, its pathogenic characteristics of the bacterial invasion from the digestive tract to settle in the intestinal submucosal lymphoid tissue, growth in macrophages and can be spread to the whole body through the bacteremia, the release of strong endotoxin, causing systemic symptoms of poisoning. Bacteria spread to the bile ducts by bacteremia can re-enter the lymphoid tissue of the intestinal wall with

bile, which can cause ulceration and hemorrhage of the intestinal wall, and even perforation.

(3) dysentery bacillus, mainly rely on the adhesion of hairs and can invade the epithelial cells of intestinal mucosa, produce endotoxin and Shiga toxin (exotoxin, Shiga dysentery bacillus) caused by pus and blood stools and systemic symptoms of poisoning.

(4) Vibrio cholerae, after oral infection, the bacteria grow on the surface of the intestinal mucosal epithelial cells and produce cholera enterotoxin, which promotes the secretory function of the cells and causes severe watery diarrhea.