A pathobiont is an organism that is native to the host's microbiome that under certain environmental or genetic changes can become pathogenic and induce disease. ^[1]

Pathobionts differ from opportunistic pathogens in the sense that they are normally native to the microbiome, where opportunistic pathogens are acquired from outside that microbiome. ^[2]

Etymology

The term was originally coined in 2008 by Sarkis Mazmanian to describe Helicobacter hepaticus and its ability to cause colitis under certain environmental conditions. ^[3]

The term pathobiont had mixed reception among the microbiology field. The main argument against using the term is that some bacteria labelled as a "pathobiont" also exhibit beneficial effects to hosts under normal conditions. ^[1] The notion that their pathogenesis is tied to environmental or genetic changes from a perceived normal state would point to a firm understanding of a normal gut microbiome, which can vary drastically. ^[1] Arguers against the term state all bacteria have metabolism that are environmentally dependent, and even symbionts have been shown to exhibit deleterious clinical effects under certain conditions. ^[1] The argument has led to the development of a proposed term, pathogenic potential to describe a microbe's ability to cause disease. ^[4] Both terms are currently used within the field.

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