The sensitivity of a number of cell cultures to different strains of Rickettsia prowazekii

: The sensitivity of some cell cultures to different R. prowazekii strains (strain E with low pathogenicity, virulent strain Breinl, strains ERifRI and EVir) has been studied with a view to the selection of an adequate culture for growing these strains and the study of their biological properties. Experiments on titration in cells have revealed that 6- to 7-day primary and secondary irradiated quail fibroblasts and human amnion cells FL show the maximum sensitivity to all strains under study, comparable to that of chick embryos. The sensitivity of 6- to 7-day primary and secondary irradiated chick fibroblasts is faintly pronounced, and 24-hour chick and quail fibroblasts are still less sensitive. Cells FL have shown high sensitivity to strain E and mutant ERifRI in prolonged subculturing for 140 and 63 days (the term of observation) respectively after a single inoculation.