POS0249 THE EFFECT OF NASAL STAPHYLOCOCCUS AUREUS COLONIZATION ON DISEASE ACTIVITY AND THE EFFECT OF ANTIBIOTIC TREATMENT IN PATIENTS WITH ANCA ASSOCIATED VASCULITIS; A RETROSPECTIVE COHORT STUDY

Background:Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) is a necrotizing vasculitis, predominantly affecting small or medium vessels with few or no immune deposits. Ear, nose and throat (ENT) involvement in AAV is frequently present. AAV has a relapsing-remitting disease course. A factor that has been associated with induction of relapses is nasal Staphylococcus aureus (S. aureus) colonization. This alleged association between nasal colonization and induction of relapses has resulted in the use of antibiotics. However, the effect of antibiotic treatment on disease activity remains controversial. Some studies showed a beneficial effect of antibiotic treatment whereas other studies found no effect of antibiotic treatment on disease activity.Objectives:The aim of this study was to identify the role of nasal S. aureus colonization and the effect of systemic or local antibiotic treatment on disease activity in patients with AAV.Methods:Clinical, laboratory and histological data from all AAV patients with ENT involvement, diagnosed in two medical centers 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 antibiotics (mupirocin) use was collected. Disease activity was divided into systemic and local disease activity. Systemic disease activity consisted of history of relapses, relapse number per patient years and Birmingham vasculitis activity score version 3 (BVAS3) at last visit. Local disease activity included history of ENT relapses, development of saddle nose deformity or subglottic stenosis during follow-up.Results:Two-hundred and thirteen patients were included in the analysis. Median follow-up time was 8 (IQR 3 -17) years. S. aureus colonization was tested in 100 (46.9%) cases of which 44 patients tested positive. Only one patient developed a subglottic stenosis, and 13 patients developed a saddle nose deformity during follow-up. Systemic and local disease activity at baseline and at last visit were comparable between patients with and without and S. aureus colonization. Regression analysis showed no difference in relapse number per patient year between AAV patients colonized with S. aureus versus non-colonized patients (RR 2.03; 95%CI, 0.97 – 4.26, p=0.06). This also accounted for local ENT relapses (OR 0.134; 95%CI 0.06-1.47, p=0.14) and saddle nose deformity (OR 0.61; 95%CI 0.04-10.68, p=0.74). Twenty-eight (13.1%) S. aureus positive patients received antibiotics aimed at eradication of S. aureus. Twenty-two (10.3%) received cotrimoxazole, 2 (0.9%) received azithromycin and 17 (8.0%) patients received mupirocin ointment. No significant difference was found between the treated versus non-treated group with regard to systemic and local disease activity.Conclusion:Nasal S. aureus colonization does not influence systemic or local disease activity. Antibiotic eradication treatment did not modify disease activity in this study.Table 1.Effect of AB treatment on disease activity of 40 AAV patients with ENT involvement and S. aureus colonizationDisease activityAntibiotic treatmentP-valueYes (n=28)No (n=12)Systemic symptomsHistory of one or more relapses, n (%)18 (47.4%)4 (10.5%)0.635Relapse number per patient years, median (IQR) *0.11 (0-0.18)0.17 (0.02 – 0.26)0.346BVAS3 last visit, median (IQR)1 (0-4)1 (0-4)0.932Local symptomsHistory of one or more ENT relapses, n(%) *9 (33.3%)3 (11.1%)0.438Development of saddle nose deformity during follow-up, n (%) *4 (12.1%)0 (0%)0.367Values are median (interquartile range IQR) or n (%). BVAS3: Birmingham Vasculitis Activity Score version 3; ANCA: Anti-Neutrophilic Cytoplasmic Autoantibody; AAV: ANCA associated vasculitis; ENT: ear, nose and throat. * More than 10% missings in analysis. For an overview of the number of included patients per analysis, see supplementary table B.Disclosure of Interests:None declared