Pneumonia caused by Nocardia species.

There are nine species of Nocardia. Nocardia asteroides accounts for 80% of infections caused by this organism in man. N brasiliensis causes 3% to 9% of these infections, and N farcinica is being recognized with increasing frequency. We present three cases of Nocardia pneumonia two of which were caused by N asteroides and one was caused by N farcinica. These cases illustrate the diverse nature of nocardiosis and show that sometimes it is difficult to determine whether the Nocardia was community- or nosocomially-acquired.