New bacterial agent of pneumonia isolated from renal-transplant recipients.

A gram-negative, weakly acid-fast bacillus has been isolated in embryonated eggs and in guineapigs from lung tissue of two renal-transplant recipients with acute purulent pneumonia. Culture of infected lung tissue and subculture of the egg isolate on artificial media, including media for legionnaires' disease bacterium (Legionella pneumophila), failed to produce growth. Ultrastructural analysis showed that the organism is a prokaryote with a cell-wall structure typical of a gram-negative bacillus but different from that of L. pneumophila. In both patients serum antibody to both isolates developed in high titre. In its microbiological, tinctorial, and ultrastructural characteristics this bacterium differs sufficiently from L. pneumophila and other pulmonary pathogens to indicate that it may be a new agent of bacterial pneumonia.