These include direct inhibition of pathogens by beneficial microbes, through the production of bacteriocins, and indirect mechanisms involving the host, such as activation of immune defenses (for example, nucleotide-binding oligomerization domain-containing protein 2 (NOD2), which is involved in the immune response to bacterial infection) or enhancement of epithelium-derived antimicrobial peptides (for example, regenerating islet-derived III gamma (RegIIIγ)) [19]. Here, NOD2 is linked to bacterial infectious disease.