The effect of nasal Staphylococcus aureus colonization and antibiotic treatment on disease activity in ANCA-associated vasculitis: a retrospective cohort study in the Netherlands.

The aim of this study was to identify the role of nasal Staphylococcus aureus (S. aureus) colonization and the effect of systemic or local antibiotic treatment on disease activity in patients with antineutrophil cytoplasmic antibodies (ANCA) associated vasculitis and ear nose and throat (ENT) involvement. Clinical, laboratory and histological data from all patients with ANCA-associated vasculitis and ENT involvement, who were diagnosed in two medical centres in The Netherlands between 1981 and 2020, were retrospectively collected. Nasal S. aureus colonization was defined as at least one positive nasal swab during follow-up. Data on systemic (cotrimoxazole and azithromycin) and local (mupirocin) antibiotic use were collected. Disease activity was divided into systemic and local disease activity. Univariate analyses and regression analyses (negative binomial Poisson and binary regression) were used. Two-hundred and thirteen patients were available for analysis. Median follow-up time was 8 (IQR 3-17) years. S. aureus colonization was tested in 100 (46.9%) cases of whom 44 patients (44%) tested positive. In these 100 patients, systemic and local disease activity at baseline and at last visit were comparable between patients with and without S. aureus colonization. Twenty-eight of the 44 S. aureus positive patients received antibiotics aimed at eradication of S. aureus. No statistically significant difference was found between the treated versus non-treated group with regard to systemic and local disease activity. Nasal S. aureus colonization does not influence systemic or local disease activity. Antibiotic treatment aimed at eradication did not modify disease activity.