Is There a Brain Microbiome?

Numerous studies have identified microbial sequences or epitopes in pathological and non-pathological human brain samples. It has not been resolved if these observations are artifactual, or truly represent population of the brain by microbes. Given the tempting speculation that resident microbes could play a role in the many neuropsychiatric and neurodegenerative diseases that currently lack clear etiologies, there is a strong motivation to determine the ground truth of microbial existence in living brains. Here I argue that the evidence for the presence of microbes in diseased brains is quite strong, but a compelling demonstration of resident microbes in the healthy human brain remains to be done. Dedicated animal models studies may be required to determine if there is indeed a brain microbiome.

Automated summary

Numerous studies have identified microbial sequences or epitopes in pathological and non-pathological human brain samples, but it is still uncertain whether these observations are artifactual or truly representative of brain contamination by microbes. While the evidence for the presence of microbes in diseased brains is strong, a convincing demonstration of resident microbes in the healthy human brain is still lacking. Dedicated animal model studies may be necessary to determine the existence of a brain microbiome.