Organism and Microbiome Analysis

Revisiting the controversy: The role of fungi in chronic rhinosinusitis

In the last two decades, the development of culture-independent genomic techniques has facilitated an increased appreciation of the microbiota-immunity interactions and their role in a multitude of chronic inflammatory diseases such as chronic rhinosinusitis (CRS), asthma, inflammatory bowel disease and dermatitis. While the pathologic role of bacteria in chronic inflammatory diseases is generally accepted, the understanding of the role of fungi remains controversial. Chronic rhinosinusitis, specifically the phenotype linked to nasal polyps, represents a spectrum of chronic inflammatory diseases typically characterized by a type 2 immune response. Studies on the microbiota within sinus cavities from healthy and diseased patients have focused on the bacterial community, mainly highlighting the loss of diversity associated with sinus inflammation. Within the various CRS with nasal polyps (CRSwNP) phenotypes, allergic fungal rhinosinusitis presents an opportunity to investigate the role of fungi in chronic type 2 immune responses as well as the antifungal immune pathways designed to prevent invasive fungal diseases. In this review, we examine the spectrum of fungi-associated sinus diseases highlighting the interaction between fungal species and host immune status on disease presentation. With a focus on fungi and type 2 immune response, we highlight the current knowledge and its limitations of the sinus mycobiota along with cellular interactions and activated molecular pathways linked to fungi.

The Association Between Disease Severity and Microbiome in Chronic Rhinosinusitis

OBJECTIVE

The role of the microbiome in the etiology of chronic rhinosinusitis (CRS) is still in debate. Reductions in richness and diversity have been implicated in CRS; however, limited knowledge exists regarding the impact of the severity of disease on the microbiome. The associations between constituents of the microbiome and the degree of mucosal inflammation and tissue eosinophilia are described.

METHODS

A cross-sectional study of CRS and non-CRS patients who underwent endoscopic sinus surgery was performed. Sinus mucosal biopsies were assessed for the degree of inflammation and tissue eosinophilia. Middle-meatal swabs were subjected to 16S rRNA gene sequencing, which quantified the prevalence, mean relative abundance, richness, and diversity. Comparisons between the microbiome at the genus level and degree of inflammation (absent, mild, moderate, severe) and tissue eosinophilia (absent, < 10, 10-100, > 100 per high-powered field) were performed.

RESULTS

Eight-nine patients (52.8 ± 14.21 years, 64.0% male) were assessed. Of those, 52 had CRS and 37 were controls. Corynebacterium and Staphylococcus were the most abundant genera in both the CRS (29% and 16%) and non-CRS groups (40% and 20%). Richness decreased in more severely inflamed patients (23.2 ± 13.9 vs. 18.1 ± 16.1 vs. 16.8 ± 12.3 vs. 14.7 ± 10.9; P < 0.01), as did diversity (1.4 ± 0.7 vs. 1.2 ± 1.0 vs. 1.2 ± 0.8 vs. 0.9 ± 0.7; P = 0.05). Richness was associated with higher tissue eosinophilia (23.2 ± 13.9 vs. 19.3 ± 17.2 vs. 15.9 ± 11.6 vs. 13.4 ± 6.6; P < 0.01).

CONCLUSION

The loss of richness and diversity seen in the CRS microbiome appears to be a product of severity of inflammation and tissue eosinophilia. Whether this dysbiosis is causative or a result of the disease with impaired epithelial integrity requires ongoing research.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:1265-1273, 2019.