Objectives. Nocardiosis is a rare opportunistic infection that is frequently associated with dissemination (i.e. involvement of several body sites). Identifying the factors associated with Nocardia spp. dissemination may help improving the management of patients with nocardiosis.

Methods. This 10-year (2010–2020) retrospective multicenter cohort study included adult patients with Nocardia-confirmed infections. The first objective was to determine the factors associated with disseminated nocardiosis. The secondary endpoints were to determine and compare the management and the 12-month overall mortality in patients with localized and disseminated nocardiosis. Univariate and multivariate logistic regression analyses were used.

Results. Nocardia spp. infection was confirmed in 110 patients, of whom 38 (34.5%) had disseminated nocardiosis. In univariate analysis, the factors associated with dissemination were immunosuppressive conditions: having an auto-immune disease and receiving high-dose corticosteroid (31.5% vs 8.3%, P = 0.003 and 52.6% vs 26.3%, P = 0.007, respectively). Absolute lymphocyte count <1 G/L at diagnosis was the only biomarker associated with dissemination (57.2% vs 26.3%, P = 0.007). Nocardia farcinica was not only the most frequent species identified in patient specimens (n = 22, 20%) but was also associated with a higher rate of dissemination (36.8% vs 11.1%, P = 0.002). Multivariate analysis confirmed the association between auto-immune diseases, lymphopenia, N. farcinica species and the higher rate of dissemination. Even though patients with disseminated nocardiosis were treated longer and more often with an antibiotic combination therapy, their 12-month overall mortality was significantly higher than that of patients with localized nocardiosis (36.8% vs 18%).

Conclusions. Dissemination of Nocardia spp. is favoured by auto-immune diseases, lymphopenia, and infection with N. farcinica.