Studies on the Virus of Psittacosis Cultivated in Vitro

Abstract

The virus of psittacosis has been cultivated in Li and Rivers'' fluid medium, Zinsser, FitzPatrick and Wei''s solid agar medium and propagated in the yolk sac of the developing chick embryo. American, S. American, Mexican and Australian strains have been grown with equal ease. The "Maine" strain isolated from an American parrakeet has been maintained by cultivation for 21/2 yrs. through 252 serial passages without loss of virulence. Virus multiplication is intimately associated with tissue survival. In the fluid medium the factors of utmost importance to virus multiplication are living susceptible tissues, certain physiologically essential salts and optimal tissue to fluid ratio. Under opt. conditions virus growth is a function of the incubation period and of the conc. of the inoculum. The virus of psittacosis has been observed multiplying in mesenchymal cells, fibroblasts, epidermal epithelium, liver cells and macrophages of chick embryo tissues without any peculiar affinity for certain types of cells. The fluid medium was used as a means of titrating virus suspensions; but the practicability of this method is limited by a strictly aseptic technic. It is equally as sensitive as the mouse. The microscopically discernible development stages of the psittacosis virus in cultures correspond with those reported by previous investigators. The name Microbacterium multiforme psittacosis has priority rights over the designation of L.C.L. bodies for the elementary bodies etiologically responsible for psittacosis. Virus cultures, especially on the solid agar medium, are excellent sources of material for the production of vaccines and antigens.