Metagenomic sequencing provides evidence of the nasal microbiota’s influence on idiopathic orbital myositis: a case control study

Abstract Background: Nasal microbiota is a key factor in the development of chronic rhinosinusitis (CRS). Its influence on orbital autoimmune diseases remains unknown. This study aims to investigate the influence of CRS-related nasal dysbiosis on extraocular muscle (EOM) microbiota in patients with or without idiopathic orbital myositis (IOM).Methods: Sixteen subjects were recruited, including 4 cases in each study group [IOM(+) CRS(+) group, IOM(–) CRS(+) group, IOM(+) CRS(–) group, IOM(–) CRS(–) group]. The EOM tissues and corresponding incision tissues were sampled and processed with metagenomic next-generation sequencing (mNGS). The nasal swaps from middle meatus were collected and analyzed with 16s rRNA sequencing. The sequencing data were calculated with Shannon index for microbial diversity, principal component analysis for microbial abundance and linear discriminant analysis effect size for dominant species.Results: A total of 42 species of bacteria, 3 species of fungi and no virus were detected. Both microbial diversity and microbial abundance differed between the EOM and incision samples in IOM(–) CRS(+) and IOM(–) CRS(–) subjects, with Staphylococcus predominant in the EOM samples and Micrococcus luteus predominant in the incision samples. The microbiota also differed between EOM and swap samples in the IOM(–)CRS(+) subjects, and the most distinguishable species in the swab samples was Cutibacterium acnes. Further analysis of the swab samples confirmed nasal dysbiosis in the CRS(+) subjects with Staphylococcus haemolyticus representating as the dominant species. The microbiota of EOM samples differed between the IOM(–)CRS(+) and IOM(–)CRS(–) subjects, resulting into preponderance of Cutibacterium acnes in the IOM(–)CRS(+) subjects. Small discrepancies of EOM microbiota were detected between the IOM(+)CRS(+) and IOM(+)CRS(–) subjects, but data analysis showed no statistical significance. The above findings demonstrate an alteration of EOM microbiota in CRS patients, providing evidence that nasal dysbiosis may play a role in regulating microbial communities in EOM.Conclusions: This study provided a reference spectrum of EOM microbiota in IOM patients and offered insights into the nasal microbiota’s influence on orbital autoimmune conditions.(Trial registration: Chinese Clinical Trial Registry, ChiCTR2100047731. Registered 24 June 2021 - Retrospectively registered, https://www.chictr.org.cn/showproj.aspx?proj=127896)