Separate attempts were made to cultivate the virus of typhus fever from the blood of 10 cases of endemic typhus. Dextrose-cystine-brain-veal agar, a medium known to be suitable for the cultivation of Past. tularensis was used. Incubation was carried out aerobically and under conditions of reduced oxygen tension. Gram-positive diphtheroids were obtained in 6 of the 10 cases. In 2 of these 10 cases a Gram-negative rod belonging to the proteus group was obtained. None of these organisms produced signs or symptoms of typhus when inoculated into guinea pigs. The same animals were not immune to typhus passage virus.
Attempts to cultivate the virus from blood cultures or infected tissue (guinea pig tunica vaginalis) on Kendall's “K” medium, both liquid and solid, were completely unsuccessful.
A strain of B. proteus (American Type Culture No. 881) carried through ten generations on liquid K media with both daily and weekly transfers did not become pathogenic for guinea pigs. The same animals were not afterwards found to be immune to passage virus.
Additional evidence obtained from tissue culture seems to show that the virus is an obligatory parasite.
Cultivation in the living animal body (Zinsser and Castaneda) seems to offer the best means for developing quantities of the virus.
Promising results with vaccines prepared from this source have been achieved by Zinsser and Castaneda in animals and by Sanchez-Casco in the human organism.