Our recent piece on the nation's first stool bank touched upon the burgeoning field of microbiomics — exploring the "rain forest" of varied species among the trillions of bacteria that inhabit our bodies.
Advanced sequencing of the microbiome – the genome of the entire microbial population – in tissue samples taken from sites at the beginning and the end of the large intestine revealed a significant decrease in diversity in the microbial population of the Crohn's patients, who had yet to receive any treatment for their disease. The samples revealed an abnormal increase in the proportion of inflammatory organisms in Crohn's patients and a drop in noninflammatory and beneficial species, compared with the control participants. The imbalance was even greater in patients whose symptoms were more severe and those who had markers of inflammatory activity in tissue samples.
"These results identifying the association of specific bacterial groups with Crohn's disease provide opportunities to mine the Crohn's-disease-associated microbiome to develop diagnostics and therapeutic leads," said senior author Ramnik Xavier, MD, PhD, chief of the MGH Gastrointestinal Unit and director of the MGH Center for the Study of Inflammatory Bowel Disease.
Antibiotics are often prescribed for symptoms suggestive of Crohn's before a diagnosis is made, but in participants who happened to be taking antibiotics at the time samples were taken, the microbial imbalance was even more pronounced, suggesting that the antibiotic use could actually exacerbate symptoms rather than relieve them, the authors note. Next steps will be to uncover the function of these microbes and their products and to learn how the microbiome and microbial products interact with the patient's immune system, with the possibility that these interactions could represent the molecular basis for the disease.