Chronic rhinosinusitis microbiome and mucin enrichment

Chronic rhinosinusitis (CRS) is a prolonged and difficult-to-treat inflammatory condition of the human paranasal sinuses. Bacteria are thought to be a key part of CRS pathogenesis. Staphylococcus aureus is a frequently isolated bacterium from CRS, however its presence asymptomatically in the nasal cavity of ~50% of adults suggests extrinsic and host variables are determinants of a commensal versus pathogenic lifestyle within the upper airways. Interbacterial interactions between S. aureus and co-colonizing bacteria have not been investigated for a mechanistic role of bacterial pathogenesis in CRS. Anaerobic bacteria have also been identified to be associated with the progression of CRS and resistance to antibiotic treatment, suggesting the presence of these organisms confer functions that contribute to pathogenesis, including effects on S. aureus physiology. The study aimed to use 16S rRNA gene sequencing of the V4 region to characterize the microbiome of sinus mucus from patients with chronic rhinosinusitis. We hypothesized that the anaerobic bacteria in CRS sinus mucus used mucin glycoproteins, highly expressed in CRS, as a source of nutrients. Enrichment of CRS sinus mucus on a minimal medium with mucins as the sole nutrient source demonstrated that mucins can support the growth of CRS-associated anaerobic communities. Furthermore, we show using growth assays and RNA-seq that mucin degradation by these consortia impacts the growth and global gene transcription of Staphylococcus aureus LAC USA300. These results are the first to describe mucin-degradation as a metabolic characteristic of anaerobic bacteria in CRS. This work reveals a disease mechanism whereby microbial dysbiosis may have critical implications for the onset, progression, and treatment of S. aureus-associated CRS.