The isolation from beef serum of a survival factor for Treponema pallidum.

The problem of the cultivation in vitro of virulent Treponema pallidurn has been approached in this laboratory by investigations of the physical and chemical factors which influence the survival of this organism in artificial media. A previous report (1) described techniques which permitted the isolation of T. paZZidum in a relatively tissue-free state from rabbit testicular syphilomas. These organisms survived in vitro and retained virulence for a period of several days. As a medium consisting of known constituents’ was used for the extraction of the testes, the only unknown substances available to the organisms were those derived from the testicular tissue. It was found that this tissue extract was necessary for the survival of T. pallidurn, since the organisms when centrifuged and resuspended in the basal medium would survive for only 12 to 24 hours. After the addition of either normal rabbit or bull testicular tissue extracts or ultrafiltrate of beef serum2 to the medium used for resuspending T. pallidurn survival was supported for 5 to 8 days. Similar effects of serum ultrafiltrate have been reported by Eagle and Steinman (2). It was found that mixtures of the known vitamins, glucose and other sugars, amino acids, and various purines and pyrimidines would not substitute3 for the testicular extract or the serum ultrafiltrate and hence it appeared likely that the effect of the ultrafiltrate of serum or the testicular extract was due to a hitherto unrecognized component of blood or tissue extracts.