Plaque Formation by Rickettsia conori in WI-38, DBS-FRhL-2, L-929, HeLa, and Chicken Embryo Cells

Abstract

Mammalian cells particularly suitable for the study of specialized aspects of rickettsial biology were tested for their ability to support plaque formation by Rickettsia conori . The detection of plaques was substantially influenced by the combination of growth medium and cell type used. Large plaques (2.0 to 3.0 mm in diameter) occurred by 8 days postinfection in WI-38 and DBS-FRhL-2 cells supported by medium 199. Smaller plaques (0.5 to 1.0 mm in diameter) were seen in L-929 and HeLa cells at 8 to 11 days postinfection and were more discernible in cells supported with Eagle minimal essential medium. Chicken embryo cells maintained in Dulbecco's modified Eagle medium exhibited large spherical plaques with a diameter of approximately 1.5 mm by 8 days postinfection.