Characterising the allergic fungal rhinosinusitis microenvironment using full-length 16S rRNA gene amplicon sequencing and fungal ITS sequencing

Introduction: Allergic fungal rhinosinusitis (AFRS) is a severe phenotype of chronic rhinosinusitis with nasal polyposis (CRSwNP), characterised by localised and exaggerated type 2 inflammation. While fungal antigenic stimulation of unregulated Th2-mediated inflammation is the core pathophysiological mechanism, the direct and synergistic role of bacteria in disease modification is a pervasive hypothesis. We set out to define the microenvironment of AFRS to elucidate virulent organisms that may be implicated in the pathophysiology of AFRS. Methodology: We undertook a cross-sectional study of AFRS patients and non-fungal CRSwNP patients. Demographics, disease severity, culture and microbiome sequences were analysed. Multimodality microbiome sequencing included short-read next-generation sequencing (NGS) on the Illumina Miseq (16S rRNA and ITS) and full-length 16S rRNA sequencing on the Oxford Nanopore Technologies GridION (ONT). Results: Thirty-two AFRS and 29 non-fungal CRSwNP patients (NF) were included in this study. Staphylococcus aureus was the dominant organism cultured and sequenced in both AFRS and NF groups (AFRS 27.54%; NF 18.04%; p = .07). Streptococcus pneumoniae (AFRS 12.31%; NF 0.98%; p = .03) and Haemophilus influenzae (AFRS 15.03%; NF 0.24%; p = .005) were significantly more abundant in AFRS. Bacterial diversity (Shannon's index) was considerably lower in AFRS relative to NF (AFRS 0.6; NF 1.0, p = .008). Aspergillus was the most cultured fungus in AFRS (10/32, 31.3%). The AFRS sequenced mycobiome was predominantly represented by Malassezia (43.6%), Curvularia (18.5%) and Aspergillus (16.8%), while the NF mycobiome was nearly exclusively Malassezia (84.2%) with an absence of Aspergillus or dematiaceous fungi. Conclusion: A low diversity, dysbiotic microenvironment dominated by Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae characterised the bacterial microbiome of AFRS, with a mycobiome abundant in Malassezia, Aspergillus and Curvularia. While Staphylococcus aureus has been previously implicated in AFRS through enterotoxin superantigen potential, Streptococcus pneumoniae and Haemophilus influenzae are novel findings that may represent alternate cross-kingdom pathophysiological mechanisms.