Scanning electron microscopy of Legionella pneumophila in clinical tissue.

Scanning electron microscopy (SEM) is a valuable technique for rapid detection of the presence of microorganisms, for determination of their three-dimensional morphology and topology and for identification of their anatomical sites. It has been used for these purposes in Legionnaires' disease with three patients at autopsy in an investigation of Legionella pneumophila in situ. In two cases the study was restricted to lung, and in the third case tissues from extra-pulmonic sites were examined in addition to lung. Microorganisms in good condition of surface preservation were found in lung, tracheal lymph node and heart. The work has shown that the bacterium is pleomorphic, that it can be either rod or sausage-shaped and that it can possess a smooth, dimpled or wrinkled surface, with or without small terminal or lateral blebs. Binary fission was often seen and there was some minimal evidence of flagella in clinical specimens. Well preserved bacteria were found in lung both intra- and extracellularly.