Fecal calprotectin and gut microbiome in a cohort without intestinal pathologies from northern Italy

Fecal calprotectin is a biomarker for intestinal inflammatory conditions, while specific taxa of gut microbiota are proposed as biomarkers for inflammatory bowel disease. However, the relationship between microbiota and calprotectin levels is still largely unexplored. Using shallow shotgun metagenomics, we investigate microbial taxonomic and functional patterns correlated with calprotectin levels in fecal samples of 515 adult individuals without known intestinal pathologies, enrolled within the Parma Microbiota Project. The median value of calprotectin was 23.6 μg/g, but levels higher than the normal threshold of 50 μg/g were measured in 20% of participants. While no changes were detected in alpha- and beta-diversities, calprotectin levels were negatively associated with butyrate-producing bacteria, while positively correlated with several opportunistic pathogens. Functional analysis showed significant correlations between calprotectin levels and the predicted microbial enzymatic functions. If confirmed in longitudinal studies, these findings could indicate early microbial biomarkers of gut inflammatory conditions.