Ectopic colonization by oral bacteria as an emerging theme in health and disease.

The number of research papers published on the involvement of the oral microbiota in systemic diseases has grown exponentially over the last four years clearly demonstrating the growing interest in this field. Indeed, accumulating evidence highlights the central role of ectopic colonization by oral bacteria in numerous non-communicable diseases including inflammatory bowel diseases (IBDs), undernutrition, pre-term birth, neurological diseases, liver diseases, lung diseases, heart diseases or colonic cancer. There is thus much interest in understanding the molecular mechanisms that lead to the colonization and maintenance of ectopic oral bacteria. The aim of this review is to summarize and conceptualize the current knowledge about ectopic colonization by oral bacteria, highlight wherever possible the underlying molecular mechanisms and describe its implication in health and disease. The focus lies on the newly discovered molecular mechanisms, showcasing shared pathophysiological mechanisms across different body sites and syndromes and highlighting open questions in the field regarding the pathway from oral microbiota dysbiosis to non-communicable diseases.