The gross lung photo above shows multiple abscesses due to infection with Nocardia asteroides. The organism is gram-positive but, in contrast to A. israelii, it stains red with a modified acid-fast stain (right photo) and is aerobic.
Nocardia, the cause of chronic, suppurative infections, is found in the soil. N. asteroides infection usually originates in the lungs from where it may spread. N. brasiliensis infects the skin. The disease can be seen in immunocompetent patients but much more likely in the immunocompromised.
From the slide collection of the late Dr. Charles Kuhn