Chronic nasal Staphylococcus aureus carriage identifies a subset of newly diagnosed granulomatosis with polyangiitis patients with high relapse rate

Abstract

Objective: The aim of this study was to evaluate whether chronic nasal carriage of Staphylococcus aureus (SA) is related to relapses in patients with newly diagnosed ANCA-associated vasculitis (AAV).

Methods: In two clinical trials (n = 200), for early systemic (n = 83) and generalized (n = 117) AAV, nasal swabs were obtained monthly and at the time of a relapse. Chronic nasal SA carriage (CNSAC) was defined as ⩾ 75% of cultures being SA positive, with non-carriers being SA negative in all cultures and remaining patients being intermittent carriers. Fifty-five of 200 (27.5%) patients received prophylactic trimethoprim/sulfamethoxazole (T/S) against Pneumocystis jirovecii .

Results: Of the total AAV patients, 24/200 (12%) were chronic, 102/200 (51%) intermittent and 74/200 (37%) non-carriers. Of 65 relapsing patients, 10/24 (41.7%) were chronic, 32/102 (31.4%) intermittent and 23/74 (31.1%) non-carriers (P = 0.59). For all AAV patients, CNSAC was not associated with an increased relapse risk [odds ratio (OR) = 1.57, 95% CI: 0.66, 3.76; P = 0.31]. However, 23/24 chronic carriers had granulomatosis with polyangiitis (GPA). In the 73 patients with generalized GPA (hazard ratio = 4.10, 95% CI: 1.37, 12.25; P = 0.01) and the 78 patients with early systemic GPA during immunosuppression (hazard ratio = 2.73, 95% CI: 0.95, 7.87; P = 0.06), relapse rates were higher for chronic SA carriers. Prophylactic T/S was not associated with a reduced relapse risk (OR = 0.71, 95% CI: 0.36, 1.41; P = 0.33). Nevertheless, prophylactic T/S reduced CNSAC (OR = 0.19, 95% CI: 0.04, 0.91; P = 0.04).

Conclusion: The frequency of CNSAC in newly diagnosed GPA paralleled that in the general population. This subset of GPA patients (23/151, 15.2%) has a high relapse rate despite immunosuppression and prophylactic T/S treatment, requiring further investigations on pathogenesis and therapy.

Keywords: Staphylococcus aureus; chronic nasal carriage; disease activity; disease severity; granulomatosis with polyangiitis; microscopic polyangiitis; nasal culture; relapse; trimethoprim/sulfamethoxazole; vasculitis.