the maximum plaque formation was observed under the following conditions : the monolayer of chick fibroblasts ( seeding density was not less than 375,000 cells per 1 sq . cm ) was grown in medium 199 with 5-10 % of fresh fetal or calf serum and inoculated with rickettsiae suspended in heart-brain infusion ;
C0016030
fibroblasts
C0007634
cells