Opportunistic pneumonia caused by a new acid-fast bacterium.

An 80-year-old black woman with a clinical diagnosis of unclassified malignant lymphoproliferative disease experienced acute pneumonia four days after chemotherapy was begun. Open lung biopsy revealed acute suppurative pneumonia with dense neutrophilic alveolar infiltrates but without granulomas or caseous necrosis. Numerous intra- and extracellular gram-negative bacilli were present, some of which were acid-fast. Routine bacterial, fungal, and mycobacterial cultures were negative. The organism was successfully cultivated by embryonated egg inoculation with subsequent transfer to buffered charcoal yeast extract agar. Serologic studies using the indirect fluorescent antibody technic confirmed the presence of an organism recently described as the "Pittsburgh pneumonia agent," further suggesting that this particular organism is a significant cause of suppurative pneumonia in the immunocompromised host.