A light and electron microscopic examination of Ehrlichia sennetsu in cultured human endothelial cells.

Umbilical cord-derived human endothelial cells were used for the propagation of Ehrlichia sennetsu. Scanning electron microscopic studies revealed numerous pleomorphic ehrlichiae extending from the surface of infected human endothelial cells. Transmission electron microscopic examination of the cells revealed E. sennetsu-induced cytopathic changes at the ultrastructural level. Ehrlichiae of variable size, shape and density were located individually and in clusters enclosed within membrane lined vacuoles. The cultured human endothelial cell provides an optimal environment for the growth of E. sennetsu and is a suitable in vitro model for the study of the cytopathic effects of this human pathogen.