A recent study analyzing the intestinal microbiota in new-onset cases of Crohn's disease provides insights into patterns of dysbiosis associated with Crohn's and a means with which to diagnosis the disease.

Several studies have reported that Crohn's disease is associated with an alteration in the composition of the intestinal microbiota. However, several factors, including small sample size, the use of patients with established disease and reliance on sampling from a single site, has made physicians question their relevance to clinical application.

Ramnik J. Xavier and his colleagues (Cell Host Microbe 15, 382–392, 2014) assessed a large group of treatment-naive, new-onset cases of Crohn's disease. By assessing both the intestinal mucosal and lumen-associated microbiota, they found that there was a reduction in species richness and alterations in the abundance of several bacteria in comparison to microbiota from healthy individuals. By assessing both fecal and tissue samples, they found that these changes in the microbiota were not well-reflected in the stool samples. With receiver operating characteristic (ROC) analysis, samples from the ileum, and to a lesser extent, rectal biopsies, could be used to diagnose disease. Dysbiosis also correlated with disease severity and was exacerbated with antibiotic usage. Taken together, these findings suggest future studies are warranted to examine whether dysbiosis can be used to diagnose disease at an early stage.