Pulmonary nocardiosis associated with Klebsiella pneumoniae infection

Abstract Pulmonary nocardiosis is a rare infection that primarily affects immunocompromised individuals. Its manifestations and radiological findings are nonspecific, making diagnosis difficult and delayed. We present the case of a 75-year-old man who presented with respiratory symptoms and fever. Chest computed tomography revealed nodular and micronodular images with a tree-in-bud pattern, bilateral cavitations, and areas of consolidation. Tracheal aspiration by fiberoptic bronchoscopy with bronchoalveolar lavage was performed, from which Nocardia sp. was isolated. Sputum culture showed growth of Klebsiella pneumoniae, therefore trimethoprim-sulfamethoxazole was prescribed until the regimen was completed and regular clinical follow-up was provided. Accurate interpretation of radiological findings in the context of clinical evaluation is essential for diagnostic suspicion, therefore the use of microbiological techniques and knowledge of the epidemiology and pathogenesis of the disease are essential for a definitive diagnosis and appropriate treatment.