Clostridium difficile(CD) is an obligate anaerobic gram-positive bacillus, which is a normal flora in the human body. Other flora will be inhibited from multiplying due to the antibiotics used in large doses, and CD reproduces in the human body in large quantities. CD is divided into toxin-producing and non-toxin-producing species. All CD species produce glutamate dedrogenase (GDH) when they reproduce, and only toxigenic strains are pathogenic. Toxin-producing strains can produce two toxins, A and B. Toxin A is an enterotoxin, which can cause inflammation of the intestinal wall, cell infiltration, increased permeability of the intestinal wall, hemorrhage and necrosis. Toxin B is a cytotoxin, which damages the cytoskeleton, causes cell pyknosis and necrosis, and directly damages intestinal parietal cells, resulting in diarrhea and pseudomembranous colitis.