title: Study of the possibility of selection of the avirulent strain Rickettsia prowazeki E in cocultivation with a virulent strain of Rickettsia prowazeki in chick embryos.
mesh_terms: D000818:Animals; D001431:Bacteriological Techniques; D002642:Chick Embryo; D005827:Genetics, Microbial; D006168:Guinea Pigs; D009154:Mutation; D012283:Rickettsia prowazekii / Q000254:growth & development / Q000472:pathogenicity*; D013045:Species Specificity; D014774:Virulence