[A case of pulmonary nocardiosis due to Nocardia cyriacigeorgica with prompt diagnosis by gram stain].

An 82-year-old woman with a past history of a colectomy for colon cancer was admitted to our hospital because of fever and cough. Her chest radiologic images on admission showed bilateral pulmonary infiltration, which suggested community-acquired pneumonia. However, the results of gram and acid-fast staining demonstrated branching acid-bacilli, which suggested pulmonary nocardiosis. We administered sulfamethoxazole-trimethoprim, and her condition and radiology findings promptly improved. Nocardia cyriacigeorgica was identified from her sputum. One of the nocardial isolates, formerly identified as Nocardia asteroides, has recently been reclassified as Nocardia cyriacigeorgica by the 16S rRNA gene amplification method. Pulmonary nocardiosis may be misidentified as "aspiration pneumonia", especially in elderly people. It is important for patients with community-acquired pneumonia to be evaluated with sputum gram staining for accurate diagnosis.