Inflammatory bowel disease (IBD) is considered to result from interplay between host and intestinal microbiota. Recently it was shown that the microbiota varied along a gradient of increasing intestinal inflammation (indicated by calprotectin levels), which was associated with reduced microbial richness, abundance of butyrate producers, and relative abundance of Gram-positive bacteria (especially Clostridium clusters IV and XIVa). A significant association between microbiota composition and inflammation was indicated by a set of bacterial groups predicting the calprotectin levels. So, intestinal microbiota may represent a potential biomarker for correlating the level of inflammation and therapeutic responses but this needs to be further validated.