Invasive Nocardiosis Versus Colonization at a Tertiary Care Center: Clinical and Radiological Characteristics.

Objective: To describe the clinical and radiographic findings in a large cohort of patients with positive cultures for emphasizing the differences between invasive disease and colonization.

Patients And Methods: We conducted a single-center, retrospective cohort study of 133 patients with a positive isolate between August 1, 1998, and November 30, 2018, and a computed tomography (CT) of the chest within 30 days before or after the bacteria isolation date.

Results: Patients with colonization were older (71 vs 65 years; =.004), frequently with chronic obstructive pulmonary disease (56.8% vs 16.9%; <.001) and coronary artery disease (47.7% vs 27%, =.021), and had isolated exclusively from lung specimens (100% vs 83.1%; =.003). On CT of the chest, they had frequent airway disease (84.1% vs 51.7%; <.001). Patients with invasive nocardiosis had significantly (<.05) more diabetes, chronic kidney disease, solid organ transplant, use of corticosteroids, antirejection drugs, and prophylactic sulfa. They had more fever (25.8% vs 2.3%; <.001), cutaneous lesions (14.6% vs 0%; =.005), fatigue (18% vs 0%; =.001), pulmonary nodules (52.8% vs 27.3%; =.006), and free-flowing pleural fluid (63.6% vs 29.4%; =.024). The patterns of nodule distribution were different-diffuse for invasive nocardiosis and peribronchiolar for colonization.

Conclusion: The isolation of in sputum from a patient with respiratory symptoms does not equal active infection. Only by combining clinical and chest CT findings, one could better differentiate between invasive nocardiosis and colonization.