Extrathoracic localization of Legionella pneumophila in Legionnaires' pneumonia.

Extrathoracic organs of 12 fatal cases of Legionnaires' disease from the 1977 Vermont epidemic were reviewed for the presence of Legionella pneumophila. The bacteria were identified by direct immunofluorescence microscopy of paraffin-embedded spleen, liver, lymph node, and kidney tissue. Extrathoracic bacteria were demonstrated in six of the 12 cases (3/7 spleens, 2/9 livers, and 2/10 kidneys). In the liver and spleen, the legionellae were associated with cells of the reticuloendothelial system. In the kidney, the bacteria were restricted to the interstitium and renal tubules. There were no acute inflammatory lesions in any of these organs. The distribution of bacteria in the extrathoracic viscera is compatible with dissemination through the blood stream.