The Sinonasal Microbiome in ENP

Eosinophilic nasal polyposis (ENP) is a chronic inflammatory disorder of the upper airways characterized by a complex interplay between barrier dysfunction, type 2 immune response, and microbial dysbiosis. While traditional research focused primarily on individual pathogens, modern metagenomic approaches have redefined ENP as an ecological imbalance within the sinonasal microbiome. This chapter explores the current understanding of the microbial landscape in ENP, highlighting the shift from high-diversity commensal communities toward a low-diversity ecosystem often dominated by Staphylococcus aureus and other pathobionts. We discuss the mechanisms by which dysbiosis reinforces the inflammatory cycle, including the role of bacterial superantigens, the impact of biofilm formation on surgical outcomes, and the loss of protective metabolites such as short-chain fatty acids. Furthermore, the chapter examines how current therapeutic strategies, ranging from endoscopic sinus surgery to the recent introduction of biologicals, influence and “reset” the sinonasal microenvironment. Emerging evidence suggests that restoring microbial homeostasis may represent not only a consequence of treatment but also a potential target for sustained disease control. Finally, we review the potential for microbiome-based interventions, such as topical probiotics and precision antibiotic stewardship, to provide personalized care for patients with recalcitrant ENP.