Evaluation of darkfield and immunofluorescent techniques for demonstrating Treponema pallidum in fluids with small numbers of organisms.

Spiral organisms that are morphologically indistinguishable from Treponema pallidum and react with fluorescein-tagged, anti-T. pallidum rabbit globulin have recently been detected in the aqueous humour (AH) and cerebrospinal fluid (CSF) of syphilitics (Girard, Goldman, Baumstark, and Stickle, 1967; Goldman and Girard, 1968; Smith and Israel, 1967a, b; Wells and Smith, 1967; Wilkinson and Jones, 1967). The organisms, which may or may not be motile, are few in number and difficult to demonstrate despite prolonged microscopical examination. This paper evaluates a microhaematocrit-tube centrifugation method for the concentration of small numbers of T. pallidum and the relative efficiencies of direct immunofluorescent and darkfield examinations based on the recovery of known numbers of organisms.