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Protection Against Pathogens

Beneficial roles of the microbiome: Protection against Pathogens

The gut bacteria help to protect the integrity of the intestinal barrier by both passive and active means. Evidence suggests 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 inducing tolerance of the surrounding environment.

At the same time, the mere 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 diarrhoea, which poses a severe threat to hospital patients. C. difficile is a bacterial species that normally lives quite happily in the intestine without any 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 diarrhoea with potentially serious complications including death. A similar mechanism is responsible for the increase in yeast infections following antibiotic therapy. C. albicans is a fungus that normally lives on the body without causing any harm, but with antibiotic elimination of the normal microbiota it can expand to dominate new environmental niches and cause disease.

The microbiota are therefore crucial for normal and healthy intestinal function.