Infectious Diseases

One of the most important beneficial roles of the microbiome is its ability to protect against infection with dangerous microbes from the environment. The bacteria in the gut protect the integrity of our intestines by both passive and active means. It seems that friendly bacteria actually "talk" to the cells in the intestine, communicating when there are breaches to be repaired. These bacteria also talk to gut immune cells, preventing inflammation and promoting tolerance of the surrounding environment. At the same time, the simple presence of friendly bacteria helps prevent more dangerous microbes from causing disease. Competition with friendly bacteria for space and nutrients in the intestine is a major hurdle for harmful bacteria to overcome, and they often don't succeed. The importance of this passive protection by friendly bacteria is illustrated by the alarming example of antibiotic-induced diarrhea, which poses a severe threat to hospital patients. C. difficile is a bacterial species that normally lives quite happily in the intestine without causing problems, but is largely resistant to antibiotic treatment. Long-term antibiotic treatment kills other friendly bacteria, upsetting the normal balance and allowing rampant growth of C. difficile. Given free reign in the intestine, the bacteria cause severe diarrhea with potentially serious complications including death. The microbiota are therefore crucial for normal and healthy intestinal function and protection against pathogens.