Staphylococcus and the Microbiome in Chronic Rhinosinusitis

Abstract

Chronic rhinosinusitis (CRS) is a clinical condition resulting in prolonged inflammation of the sinonasal mucosa. Typical symptoms include nasal obstruction and discharge, facial pain, or olfactory dysfunction. These symptoms are sometimes alleviated by treatment with antibiotics, nasal steroids or saline nasal irrigation; however, in severe cases endoscopic surgery is required. CRS is common within the Western world, where it affects ~5% of the population. Despite its prevalence, the etiology and pathogenesis of CRS remains unclear, partially due to its heterogeneous nature of disease presentation. As a result, numerous host and exogenouslybased mechanisms have been hypothesised. The sinonasal microbiota has been implicated in CRS pathogenesis, particularly related to the presence of absence of Staphylococcus aureus. Staphylococcus epidermidis is also prevalent within the sinonasal microbiota and has been shown to potentially inhibit S. aureus biofilm formation. The first part of this study used Illumina sequencing targeted at the bacterial 16S rRNA gene of healthy and CRS-affected individuals to investigate the structure and diversity of the sinonasal microbiota. Quantitative PCR using species-specific and bacterial 16S rRNA primers was used for absolute quantification of S. aureus, S. epidermidis, and bacterial load. Results suggested that sinus microbiota composition was not significantly different between healthy and CRS-affected individuals. S. aureus and S. epidermidis abundance was not correlated with CRS, yet bacterial load was significantly higher in CRS-affected patients. The second part of this study aimed to compare the effects of intranasal Augmentin treatment and/or bacterial inoculation with Pseudomonas aeruginosa and Corynebacterium tuberculostearicum, two species whose presence is positively correlated with CRS, on the mouse sinus, lung, and gut microbiota composition as part of broader research efforts to develop a new mouse model of CRS. All treatments did not influence gut microbiota composition whilst sinus and lung communities could not be described due to the low proportion of reads taxonomically identified past Domain level. This study contributes to current knowledge surrounding the composition of human microbial communities in CRS and is hoped to aid in efforts to improve the quality of life for individuals suffering from CRS.