The Serologic Relationships Between Five Cultured Strains of Supposed T. Pallidum (Noguchi, Kroó, Nichols, Reiter and Kazan) and Two Strains of Mouth Treponemata

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Abstract
Summary: On the basis of their cross-reactivity in agglutination and complement fixation tests with rabbit antisera, five strains of cultivated treponemata which are now non-pathogenic, but which all purport to be T. pallidum, have been found to fall into 3 distinct groups: The Nichols and Noguchi strains were serologically indistinguishable. The Reiter and Kazan strains cross-reacted, but were not identical. The Kroó strain was serologically distinct from the other four. The Reiter strain has further been shown to be serologically almost identical with 2 strains of saprophytic mouth treponemata. Although rabbits injected with these cultured treponemata developed agglutinins and complement-fixing antibodies in high titer, they did not develop positive Wassermann or flocculation tests. In both respects the antibody response differed from that obtained with suspensions of pathogenic T. pallidum. Syphilitic sera absorbed with suspensions of the Reither or Kazan strains lost all reactivity with these organisms, but their reactivity in Wassermann or flocculation tests with tissue extracts was unaffected. Rabbits “immunized” with cultured organisms proved susceptible to infection with large inocula of pathogenic T. pallidum. The data here reported indicate that the 5 cultivated strains of treponema here studied, all purporting to be T. pallidum, differ materially in their morphologic and antigenic properties from the pathogenic organism. The validity of their identification as T. pallidum is questionable.