Cindy Boer

232 | Chapter 5.2 ▲ Figure 1: Schematic representation of the gut-microbiome taxonomic abundance in the Rotter- dam Study cohort . A) overview of the number unique taxonomies detected at each level, unknown and unclassified bacteria were excluded. A) Above, as an example, the taxonomic classification for Strepto- coccus is shown. B) Donut plot of the relative abundancy in percentage (%) of the different unique phyla present in the entire dataset (n=1427) unknown and unclassified bacteria were excluded In the present study we examine stool microbiome as a proxy for the gastrointestinal-microbiome composition in relation to knee OA severity, OA-related knee pain, measured by the WOMAC-pain score, and obesity, in a large population- based cohort. We report a significant association between Streptococcus species (spp.) abundance in stool microbiome samples, knee WOMAC pain, knee inflammation, and replicate this finding in an independent cohort. Our results suggest a true relationship between the gastrointestinal microbiome, low-grade inflammation in the knee, and knee OA pain, independent of obesity.