Intracellular location of Treponema pallidum (Nichols strain) in the rabbit testis.

During investigations designed to obtain purified suspensions of virulent Treponema pallidum (Nichols strain), infected rabbit testicular tissue was routinely examined in the electron microscope. Morphologically typical T. pallidum were found intracellularly within the cytoplasmic substance of fibroblasts, interstitial and Leydig cells, and of spermatocytes. The importance of these observations to latency and treatment is discussed.