Virulence is the ability of a microorganism (pathogen) to cause damage to its host. This is done by microorganisms releasing virulence factors which are molecules produced by bacteria, fungi or viruses. These virulence factors can bind to host cells, causing damage to the immune system of the host. Gut microbiome plays an important role in protection of the host from enteric bacterial infection. As these bacteria, fungi and viruses evolve however, many pathogens have developed strategies in order to be able to outcompete the host intestinal community. This has shown to lead to infection and/or chronic diseases.