Granulomatosis with polyangiitis (GPA) was associated with an altered nasal microbial composition at both the bacterial and fungal levels, suggesting that immunosuppressive therapies and inactive disease states are linked to healthy microbial communities, according to data published in the Annals of the Rheumatic Diseases.

The cross-sectional study was designed to examine the entire community of nasal microbiota in patients with GPA compared with healthy controls using deep sequencing methods. Nasal microbial DNA was isolated from the nasal swabs of 60 participants with GPA and 41 healthy controls, and 16S rRNA and internal transcribed spacer gene sequencing were performed. The relative abundance of bacterial and fungal taxa were evaluated, along with alpha and beta diversity. The investigators sought to assess the effects of covariates, including disease activity and immunosuppressive therapies, on microbial composition.

Compared with healthy controls, participants with GPA exhibited significantly different microbial composition (P =.04) and a lower relative abundance of Propionibacterium acnes and Staphylococcus epidermidis (false discovery rate-corrected P =.02).


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Disease activity in participants with GPA was linked to a lower abundance of fungal order Malasseziales compared with participants with GPA who were in remission (P =.04) and compared with controls (P =.01). Furthermore, the use of non-glucocorticoid immunosuppressive treatment was associated with “healthy” nasal microbiota, whereas participants with GPA who were not currently receiving immunosuppressive therapy exhibited significantly more dysbiosis (P =.01). There was no difference reported in the relative abundance of Staphylococcus aureus between patients in the GPA group vs patients in the control group.

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Limitations of the study include its cross-sectional design, which renders the analysis unable to assess for interindividual heterogeneity. The investigators concluded that the findings of this analysis warrant additional exploration of host-microbe interactions in patients with GPA, which may be a first step toward elucidating the key components of the pathophysiology of the disease and identifying novel therapies.

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Reference

Rhee RL, Sreih AG, Najem CE, et al. Characterisation of the nasal microbiota in granulomatosis with polyangiitis [published online July 11, 2018]. Ann Rheum Dis. doi: 10.1136/annrheumdis-2018-213645