Experimental Pulmonary Pneumocystis Carinii Infection in Rabbits*, by Walter

Pneumocystis carinii or interstitial plasma cell pneumonia is a common human disease in Europe. Its peak incidence is between the ages of 6 weeks and 4 months with a predilection for premature or debilitated infants. The disorder appears to be contagious, occurs sporadically or in small institutional epidemics, and is characterized by progressive respiratory failure and a mortality of 20 to 25 per cent regardless of therapy. In typical cases, morphologic changes are confined to a massive consolidation of the lungs which show a marked, chiefly plasma-cellular, infiltration of the alveolar septa and a peculiar, spongy or honeycomb-like material in the alveoli. The interstices of the spongy matter contain large numbers of the organisms, Pneumocystis carinii, and a causal relationship of this agent to the disease is generally accepted. The taxonomic position of the agent is controversial. Although various techniques have been used by many different workers, the organism has never been isolated in culture. Numerous, but usually unsuccessful attempts have been made to produce the disease in experimental animals. Some workers, following the observations of Van~k and Jirovec (1), regard the organism as a protozoon while others agree with Giese (2) that it is a fungus. A recent review of the European literature has been published by Gajdusek (3). Descriptions of sporadic cases of pulmonary Pneuraocystis infection have begun to appear only recently in the North American literature (4-11) and in general their clinical and morphologic findings closely resemble those noted in Europe. A somewhat different form of the infection has been described from this laboratory in four patients in whom the disease had produced no obvious clinical manifestations and was an incidental finding at autopsy (12). In these patients the organisms, as seen in smears and sections of lung tissue, resembled in every respect those found in typical Pneumocystis pneumonia but were present only in small numbers. The lungs showed neither massive consolida-