Treponema pallidum*

Synonyms

syphilis bacterium

Classification

aerobic or microaerophilic, gram- bacteria, spirals

Diseases

Sites and Sources

Diagnostic Factors

Virulence Factors

Treatment and Prevention

Commentary

Syphilis is interesting from an historical standpoint in that there was, apparantly, no syphilis in Europe until after Columbus had been to the New World. The first epidemic began in Italy in about 1495 and spread rapidly throughout Europe. The disease was at that time quite different from the disease today in that the skin lesions were much more purulent and death occured rapidly. Although it was not immediately suggested that Columbus had brought the disease back from America, this was suggested after a period of about 30 years. However, proof that the disease existed in America before Columbus has not been forthcoming. An alternate hypothesis holds that syphilis evolved from the non-venereal treponematoses which were (and are) prevalent in Africa, and were brought to Europe with the introduction of the slave trade which occured at about the time of Columbus' first voyage. Syphilis is transmitted by sexual contact. It is thought that the organisms enter the skin through tiny breaks, aided by their rapid motility. They multiply locally and an indurated, nontender ulcer occurs at the site of innoculation, usually after 2-4 weeks. This is the primary syphilitic chancre, also known as hard chancre, and is the first stage of the disease. The lesion is literally teaming with spirochetes and demonstrating live organisms in the chancre fluid, by means of dark-field microscopy, is pathognomonic for syphilis. This primary lesion will heal by itself after 10 days-2 weeks. 1-3 months later, secondary lesions may appear as a maculopapular rash or as moist papules on the skin and mucous membranes. The rash is distinguishable by the fact that it occurs on the palms and soles. These lesions are also loaded with spirochetes and, like the primary lesion, will heal by themselves. These two stages together constitute early syphilis. Approximately one-third of cases of early syphilis will result in a spontaneous cure, and previously antibody-positive individuals will become antibody-negative. Another third of cases will become latent syphilis, with positive serologic tests indicating infection, but will never reactivate. The remaining third will progress to late or tertiary syphilis. This stage is characterized by multiorgan involvement with few organisms found in the lesions. Bone, connective tissue, central nervous system, and cardiovasular tissue may all be involved. Because so few organisms are found at this stage it is thought that the damage may result from immune mechanisms. T. pallidum is one of the few bacteria that can be transmitted from a pregnant woman to her fetus transplacentally. The transmitted disease is called congenital syphilis, and can produce still births or babies with multiple fetal abnormalities. While the clinical pattern is quite variable, the earliest sign is usually a rhinitis (snuffles). This is soon followed by a diffuse desquamative rash. The incidence of syphilis is increasing world-wide and very closely parallels the occurance of AIDS. It has even been postulated that T. pallidum is a co-factor in the developement of AIDS after HIV infection. There is no proof for this assertion, but the ulcers of primary syphilis are known to increase the transmissibility of HIV. T. pallidum, or an organism indistinguishable from it by any known immunologic or chemical test, also causes 3 diseases known as non-venereal treponematoses; bejel or endemic syphilis, yaws, and pinta. These are usually first transmitted to children, and the initial lesions commonly occur on the lips or skin, but not on the genitals. The complete sequence of the T. pallidum genome has just been elucidated, and may be seen at http://www.tigr.org/tdb/mdb/tpdb/tpdb.html or, with an accompanying very interesting commentary, in SCIENCE, 281,375 (1998). It is hypothesized that knowing the sequence will lead to the solution of many of T. pallidum's mysteries, including the mystery of its origin.