A STUDY OF RICKETTSIAE GROWN ON AGAR TISSUE CULTURES

Abstract

The paper describes in detail a new method of growing Rickettsiae on agar slants made up with double strength Tyrode soln. and either horse, beef or human serum. On these agar slants infected tissue[long dash]at first guinea pig tunica, later mouse embryo and chick embryo[long dash]was planted, and enormous yields of Rickettsiae were obtained, one agar slant yielding at least 10 or 20 times the quantity of Rickettsiae that can be obtained from the ordinary small Maitland culture. On this medium, Murine, European and Spotted Fever Rickettsiae were easily isolated and can be indefinitely carried along. A classical European strain now carried for 58 culture generations, the last 25 on the agar cultures, is still fully virulent, produces typical typhus with all its characteristics, the cultures injected into rabbits produce Weil-Felix reactions, and[long dash]formalinized as vaccine[long dash]this culture material protects guinea pigs. This method offers a completely satisfactory technique for the production of typhus vaccines on a large scale, is applicable to other fields of Rickettsia prophylaxis, and is ready for application in man as a safe method and one from which satisfactory immunization may be expected.