OPPORTUNISTIC LUNG INFECTION DUE TO PITTSBURGH PNEUMONIA AGENT

Eight immunosuppressed patients had pneumonia due to Pittsburgh Pneumonia Agent (PPA), a gram-negative, weakly acid-fast bacterium cultivatable only in embryonated eggs and guinea pigs and distinct from Legionella pneumophila. The diagnosis was established by isolation of the agent from lung or visualization of the organism in lung tissue. The clinical presentations, radiographic abnormalities and pathology were not specific. The most consistent feature associated with the disease was the recent institution of daily high-dose corticosteroid therapy in all patients. Five of the eight patients died despite broad-spectrum antibiotic and antituberculous therapy. Antimicrobial activity against PPA was demonstrated for sulfamethoxazole combined with trimethoprim, for rifampin and for erythromycin with an egg-protection assay. Serologic studies with an indirect fluorescent-antibody technic suggested that seroconversion or high titers may be a sensitive test for PPA disease. PPA appears to be a newly recognized cause of life-threatening bacterial pneumonia in immunosuppressed patients. (N Engl J Med 301:953–958, 1979) A RECENT report from this laboratory described the isolation of a unique gram-negative, weakly acid-fast bacterium from lung tissue of two renal-transplant recipients with pneumonia.1 This microorganism was tentatively designated the “Pittsburgh Pneumonia Agent” (PPA) and is distinct from Legionella pneumophila by microbiologic, tinctorial, ultrastructural and serologic criteria.1 PPA has the ultrastructural features of a gram-negative bacillus but differs from L. pneumophila in that an unusual dense band is present in the periplasmic space. PPA is cultivatable only in embryonated eggs and guinea pigs and does not grow on mediums designed for isolation of L. pneumophila. Antiserums directed against. © 1979, Massachusetts Medical Society. All rights reserved.