Treponema Pallidum (Spirochoeta Pallida) is an organism that is generally conceded to be the cause of syphilis. It has been found, by observers in all parts of the world, in the lesions of the primary and secondary stages; it is constantly present in the lesions of congenital syphilis; it is found in the blood of persons suffering from syphilis; and it is never found either in healthy individuals or in persons suffering from diseases other than syphilis. This organism is very delicate, actively motile, non-refracting, is long, thin, spiral or corkscrew shaped, with pointed ends. When stained they measure from. 6 to 15 µ long by 0.25 µ across. Occasionally much longer forms are encountered, but these consist of several parasites attached to each other end to end. They show from six to fourteen turns, which are short, clear cut, and regular. Extremely delicate flagellae have been demonstrated at the ends. No undulating membrane has been seen.

This organism stains with difficulty and, as a rule, very lightly; consequently, special methods have to be employed. In smears the best results are obtained with Giemsa's or Roman-owsky's solutions. In tissues, Levaditi's method of nitrate of silver and pyrogallic acid gives beautiful results in formalin-fixed specimens, the treponemas staining black; the tissues, yellow. The most rapid and perhaps the most reliable method for finding the treponema is the examination with dark-ground illumination. Special apparatus is needed for this. The treponemas will stand out brightly against the black background of the preparation and are easily seen. Is Gram-negative.

Fig. 99. - Syphilis, Congenital. Heart (Mallory). Treponemata pallida in connective tissue and between muscle-fibers.

Pathogenesis

This organism is, without doubt, the cause of syphilis. As stated above, it has been found in the various lesions of the disease, and, now that it can be cultivated, Koch's postulates can be fulfilled. The disease has been reproduced experimentally in the higher forms of apes.

Cultures

Until recently the treponema could not be cultivated artificially, but Noguchi has succeeded by using special methods. By inoculating syphilitic material into the testicles of rabbits he was able to get rid of contaminating organisms. Portions of this tissue are later transferred to a medium that consists of 1 part serum with 3 parts distilled water. The tubes are then incubated under anaerobic conditions. The treponemas begin to multiply after about forty-eight hours, and continue to increase slowly for four to five weeks. They attain their natural size in ten to twelve days, and later elongate and form tangled masses.

Diagnosis

The method devised by Wassermann of applying the complement fixation-test has been used very successfully in diagnosing this condition. It has been determined that if a hemolytic system be added to a mixture of extract of syphilitic liver, heated syphilitic serum, and complement, no hemolysis occurs. The method is described fully under the heading of Wassermann Reactions (see p. 185).

Spirochaeta Refringens

This organism is very commonly associated with the Treponema pallida in the syphilitic lesions, but can be distinguished readily. It is larger and longer, and in the fresh condition is highly refractile. The turns of the spiral are fewer, longer, less regular, and flattened. The impression given is that of a piece of ribbon. Its movements are more rapid than those of the Treponema pallida, and it stains easily with the ordinary dyes, and colors blue with Giemsa's solution instead of red or pink.

Spirochaeta balanitidis has been found in cases of ulcerative balanitis, and would appear to be identical with the S. refringens.

Spirochaeta plicatilis is a large, thick spirochete which stains easily. The curves are widely separated and large, and an undulatory membrane is present.

Spirochaeta Dentium

This spirochete multiplies in carious teeth, and more closely resembles the Treponema pallidum than any other species. In common with the treponema it is an organism of very delicate structure, only slightly refractile in the fresh condition, and the turns of the spiral are regular and 15 permanent. It is, however, shorter than the treponema, its average length being 4 to 10 µ, and the turns of the spiral are closer together and not so deep. It also stains more easily than the organism of syphilis. According to Noguchi, there are at least two varieties: the S. microdentium and the S. mac-rodentiuni, the former being the one that resembles the syphilitic organism. In making smears for staining or for dark-field illumination, when the lesions are in the mouth, great care must be observed in order to prevent mistakes in diagnosis.

Spirochaeta buccalis is a large organism with few undulations. Stains easily, and should give no difficulty in distinguishing between it and the Treponema pallidum.

Spirochaeta Vincenti

This spirochete, found in association with the fusiform spirilla, has the same characters as the S. buccalis. It must be regarded as either very closely related to, or identical with, that organism.

Treponema pallidulum (Spirochoeta pertenuis) is an organism very closely related to that of syphilis. It is the cause of frambesia, or yaws, a contagious and inoculable disease very common in the tropics, and characterized by papillomatous lesions that do not involve the mucous membranes.