Penetration of endothelial cell monolayers by Borrelia burgdorferi

The ability of Borrelia burgdorferi, the agent of Lyme disease, to penetrate cultured human umbilical vein endothelial cell monolayers was investigated. After 4 h of coincubation, approximately 7.7% of added bacteria passed through the host cell monolayers. Electron microscopy revealed that the borreliae entered the endothelial cells and suggested that the organisms penetrated the host monolayers primarily by passing through them.