Nocardia spp. isolation in chronic lung diseases: Are there differences between patients with pulmonary nocardiosis and Nocardia colonization?

AIMS: Chronic lung diseases are a recognized risk factor for Nocardia spp. INFECTION: Nocardia spp. isolation does not inevitably imply disease, and thus colonization must be considered. Here, we aimed to analyse the differences between pulmonary nocardiosis (PN) and Nocardia spp. colonization in patients with chronic lung diseases. METHODS AND RESULTS: A retrospective study of patients with laboratory confirmation of isolation of Nocardia spp. in at least one respiratory sample was performed. Patients with PN and Nocardia spp. colonization were compared. There were 71 patients with Nocardia spp. identification, 64.8% were male, with a mean age of 67.7 ± 11.2 years. All patients had ≥1 pre-existing chronic lung disease, and 19.7% of patients were immunocompromised. PN and Nocardia spp. colonization were considered in 26.8% and 73.2% of patients, respectively. Symptoms and chest CT findings were significantly more frequent in patients with PN (p < 0.001). During follow-up time, 12 (16.9%) patients died, 6 in PN group. Immunosuppression, constitutional symptoms, haematological malignancy and PN diagnosis were associated with significantly shorter survival times, despite only immunosuppression (HR 3.399; 95% CI 1.052-10.989) and PN diagnosis (HR 3.568; 95% CI 1.078-11.910) remained associated with a higher death risk in multivariate analysis. CONCLUSIONS: PN was associated with clinical worsening, more chest CT findings and worse clinical outcomes. SIGNIFICANCE AND IMPACT OF STUDY: Nocardia spp. isolation in chronic lung disease patients is more common than expected and the differentiation between colonization and disease is crucial.