The resident flora of bacteria present in the intestinal tract plays an important role in controlling the potential pathogens. They compete against potential invaders. The bacterial flora maintains low pH and anaerobic conditions so as to prevent the growth of any other harmful pathogen which may enter the body. The Lactobacilli present in the intestines produce large quantities of lactic acid and butyric acid which inhibits the colonization of intestine by pathogenic Escherichia coli.
