Treponema pallidum, Schaudinn, 1905.
Syn.: Spirochæta pallida.
Treponema pallidum was first described by Schaudinn and Hoffmann in 1905 under the name of Spirochæta pallida. It has also been described under the names of Spironema pallida, Microspironema pallida and Trypanosoma luis. Siegel in 1905 described an organism which he called Cytorhyctes luis and considered to be the agent of syphilis. Schaudinn reinvestigated Siegel’s work and found T. pallidum, which he considered to be the causal agent of the disease, and pronounced against Cytorhyctes luis. It is probable now that both workers were correct, for Balfour (1911) has seen the emission of minute granules or “coccoid” bodies from T. pallidum and these granules probably correspond to the C. luis of Siegel. Recently E. H. Ross, having observed a spirochæte stage in the development of Kurloff bodies, thinks that T. pallidum is a stage in the life-history of a Lymphocytozoon. MacDonagh has also described a complicated and somewhat similar cycle, but these observations require further study and confirmation.
Fig. 56.—Treponema pallidum. (After Bell, from Castellani and Chalmers.)
T. pallidum varies from 4 µ to 10 µ in length, its average length being 7 µ, while its width is usually about 0·25 µ. Longer individuals of 16 µ to 20 µ have been recorded. The body has from eight to ten spiral turns and forms a tapering process at each end (fig. 56). The organism is most difficult to stain, and its internal structure is little known. It is possibly like that of Spirochæta duttoni or S. balbianii, as the “granule shedding” observed by Balfour is strongly suggestive of the formation of resistant bodies by those spirochætes. Hoffmann (1912) has seen the formation of spores in T. pallidum.
The Treponemata occur in the primary and secondary sores, but are difficult to find in the tertiary eruptions of syphilis. Noguchi and Moore (1913) and Mott[164] (1913) have demonstrated T. pallidum in the brain in cases of general paralysis of the insane. Marie and Levaditi (1914), however, consider that the treponeme found in the brain in such cases is different from T. pallidum.
Cultivation of T. pallidum.—This has been accomplished successfully by Noguchi,[165] using a modification of his method for spirochæte cultivation, for T. pallidum is much more difficult to grow than spirochætes, being a strict anaerobe.