Causes and ways of contracting syphilis

The causes and ways of infection with syphilis are external and internal factors contributing to the development of the disease, in addition, these are the sources from which pale treponema enters the new organism, forming a defeat in it. The disease is chronic, and proceeds as a change of successive stages of development - primary, secondary and tertiary syphilis1. In some cases, the fourth stage is also isolated - neglected syphilis, when the patient develops neurosyphilis (damage to the nervous system), pathologies of the musculoskeletal system and damage to all internal organs.

Human infection occurs at the moment when the pathogen Treponema pallidum, a pale spirochete, enters the body through damaged skin or mucous membranes.

Characteristics of the microorganism treponema pallidum

According to the science of microbiology, the bacterium treponema is a form of a curved helix, namely a cylinder, twisted into 10-12 curls. One end of the cell has 3 periplasmic flagella. Treponema is determined by dyeing it with aniline dyes, for example, Romanovsky-Giemsa paint.

The study of a microorganism usually occurs using a dark-field or phase-contrast microscope. Treponema is a microaerophil, and does not grow under artificial nutrient conditions.

The antigenic structure of the microbe is associated with lipoproteins, proteins of the outer membrane. Lipoproteins are used as antigens in the Wasserman reaction process for the serological diagnosis of syphilis (the determination of specific antibodies).

The virulence of the spirochete is due to the presence of outer membrane proteins, and LPS, which show their toxic properties after release from the cell. When dividing treponema can form separate fragments that can penetrate deep into the tissues.

Pale treponema has the ability of active movement - it rotates around its axis, bends, makes translational motion.

Under the influence of oxygen, the microbe does not die, and this microorganism is not needed for respiration.

The internal structure of the microbe looks like this: the outer shell is a three-layer membrane of proteins and polysaccharides, the cell wall, and the mucopolysaccharide capsule. From the inside, the membrane of the cytoplasm, which has processes - fibrils - is attached to the membrane. It is these processes that are the “organs” that allow movement for the cell.

Antigens are mainly located in the cell wall, and are represented by lipid, carbohydrate and protein molecules.

Carrier and carrier infection

The carrier of syphilis is an infected person in whose body treponemas live and multiply. The patient may not show signs of the disease, but he will still be a carrier, dangerous to others. In the environment, outside the human body, the bacterium is not particularly resistant - at a temperature of 42 degrees above zero Celsius microorganisms die within 4-6 hours. Lowering the temperature of treponema tolerates better, she is not afraid of freezing, in the cold bacteria can live for four days. When freezing, treponema persists for up to a year.

Microorganisms are sensitive to:

  • heavy metal salts such as arsenic, bismuth, mercury;
  • ethyl alcohol;
  • alkalis;
  • acids.

The human body, with its temperature and composition of physiological fluids, is the optimal medium for the existence of a pale spirochete. The person affected by it is the only source of infection for others.

Entrance gates for infection are mucous tissues of the genital organs (external and internal), as well as the membranes of the mouth, in some cases, the skin in other parts of the body can be the “gates”.

In the body, treponema is parasitic in the tissues, and through the vascular system it moves to all internal organs. During the first two weeks, primary syphilis is defined as seronegative - the body does not detect anti-bodies to the pathogen, therefore, tests cannot yet reveal it.

In some cases, treponemas can form so-called cysts and L-forms, which retain the pathogen in the body in a latent state, due to which the disease takes on a latent form, and can manifest itself as late latent syphilis.

How pale treponema is transmitted: main transmission routes

Where does a person get syphilis? Infection of a healthy person can occur only in the presence of two conditions:

  • sufficient concentration of pale treponema in the tissue or carrier fluid;
  • the presence of damage to the skin or mucous membranes in a person exposed to infection.

The cause of the disease can be just two microorganisms that have been introduced into the human body. The more pathogens enter the body, the shorter the incubation period will be.

Violation of the integrity of the stratum corneum of the skin or the epithelium of the mucous membranes is a prerequisite for the penetration of bacteria into the body, with even minimal damage, imperceptible to the eye, is sufficient - for example, active friction can cause them. Because of this, some doctors say that infection can occur through the whole skin. Given these factors, experts note that reliable factors that accurately determine the likelihood of injury cannot be named today, so all persons who have had contact with people infected with syphilis in the last 4 months are subject to clinical examination.

Doctors call these routes of syphilis2:

  • direct: sexual, household, intrauterine, transfusion;
  • indirect: through various objects of the surrounding world containing active pathogens on their surfaces.

Of all cases of transmission of syphilis, approximately 90-95% is carried out by the direct method, and the most common of these is the sexual way, that is, infection during sex (oral, vaginal or anal). The pathogen is transmitted in any unprotected contact with the infected. A condom can delay treponema, but if the contraceptive is torn or slips off during the process, it can cause the pathogen to enter the body of an initially healthy partner. Treponema is found in vaginal secretions in women and in semen in men.

The direct non-sexual way is infection through kisses, bites, and breast milk feeding.

Direct occupational infection occurs when inspecting patients with syphilis, and affects the medical personnel who carry it out. In addition, professional infection with syphilis can be observed during operations or postmortem studies.

Transfusion syphilis - this category refers to infection that occurs through blood transfusions from diseased donors. Addicts who use disposable syringes for injections by different people can also become infected through blood. It is drug addicts who, along with sexually abused people, are most at risk of developing syphilis.

Intrauterine infection occurs during pregnancy. During this period, the fetus through the placenta receives pathogens from the mother - thus the future child becomes infected with congenital syphilis. Acquired syphilis children fall ill during the passage through infected genital tract during childbirth, that is, in the perinatal period.

A fetus with existing congenital syphilis, most often, dies in the womb, but even if it remains alive, it is born with severe pathologies.

To prevent acquired infection from the mother, a sick woman is prescribed a caesarean section, and also prohibit breastfeeding.

In an indirect way, a pale spirochete can be obtained through close household contacts with the affected, for example, using a toothbrush or dishes of the affected if there are pieces of the patient's secret on them, that is, infection occurs most often in the home, between partners and family members.

It should be noted that the infection cannot occur through airborne droplets, since in the air the treponema dies very quickly, unlike, for example, from viruses. Genetically, or by inheritance, the disease is also not transmitted - if the fetus or newborn is infected from the mother, this happens due to the direct entry of pathogens from the mother into his body.

Can you get syphilis through a handshake? Such a method of infection can occur in very rare cases if the patient has a lesion in the palm of his hand - a syphilitic chancre, and the second person has abrasions, burns, cuts on the skin of the palm. With regard to infection in public pools, baths, saunas, doctors say that the probability of catching household syphilis in this way is very small.

As for masturbation, it is possible to become infected with syphilis during masturbation only if on the hands and on the genitals there are, on the one hand, damage to the mucous membranes or skin, on the other - physiological fluids containing the causative agent of the disease.

Behavior of pale treponema at different stages of syphilis

By conducting experimental medical research, it was found that the detection of Treponema pallidum microorganisms is possible at any stage of disease formation.

The result of the incubation period from the moment of infection is the appearance of a primary syphilitic chancre. At this point, the multiplied bacteria are in the lesions, in the tissue fluid, and the patient himself is the disseminator of the infection. Pathogens are found not only in blood, but also in physiological fluids — saliva, semen, and in children with congenital syphilis — in nasal discharge. Primary period can last up to 7 weeks.

In the secondary period of infection, the pathogens reach all the internal organs, they multiply in the lymph nodes. The stage may take from 2 to 5 years.

Untreated syphilis enters a tertiary stage. At this point, treponema is present in all internal tissues, cells, vessels, bones.

Carrier contagion depends on the duration of the disease — patients with early forms are most infectious, especially in the first two years of the disease. Patients with the most advanced stages are usually less dangerous and contagious.

Risk groups: who is most susceptible to syphilis

The bulk of the population susceptible to the development of the disease - people aged 20 to 45 years. The peak incidence occurs at the age of 20 to 29 years. Even 10-20 years ago, the disease was more often recorded in men who used the services of prostitutes, now women of childbearing age are becoming more and more sick.

Persons with promiscuous sex, drug addicts, homeless people - they all represent the part of the population that has syphilis more often.

At the beginning of the last century, syphilis was catastrophic, mostly in the village. Now, a century later, the disease is equally uniformly distributed among village and city dwellers. Infection can occur through sexual contact, through blood, saliva, and even through everyday objects.

  1. ↑ ASM (American Society for Microbiology) - The biological basis of syphilis
  2. ↑ Wikipedia - Ways of transmitting syphilis
Article author:
Izvozchikova Nina Vladislavovna

Specialty: infectious diseases specialist, gastroenterologist, pulmonologist.

Total experience: 35 years.

Education: 1975-1982, 1MMI, San gig, high qualification, infectious diseases doctor.

Science degree: doctor of the highest category, PhD.


  1. Infectious diseases.
  2. Parasitic diseases.
  3. Emergency conditions.
  4. Hiv
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