Treponema pallidum

Introduction

The term "Treponema " indicates a genus of bacteria to which two different pathogenic species belong, Treponema pallidum And Treponema carateum, microorganisms involved respectively in the onset of syphilis and pinta. Although most species belonging to the genus Treponema establish a form of commensalism with the host (resulting non-pathogenic), the Treponema pallidum it is distinguished by its characteristic virulence.
Let's see in more detail the distinctive features of the Treponema pallidum.

Microbiological analysis of Treponema pallidum

Exponent of the phylum Spirochaetes and of the Spirochaetaceae family, the Treponema pallidum it is a gram negative bacterium, vector of diseases called trepomatosis among which the lue or syphilis stands out.

Observed by dark field or fluorescence microscopy, the bacterium appears as a thin, helical and spiral-shaped microorganism. It has a diameter of 0.1-0.5 microns and a variable length from 5 to 20 microns.

Treponema pallidum it is a bacterium sensitive to heat and dry temperatures. In reference to the very poor ability to survive in an oxygen-rich environment, it is defined as a "microaerophilic" bacterium.
Although it is endowed with flagella, the Treponema pallidum it differs from other flagellated microorganisms: in fact, these cellular appendages used for motility are called endoflagelli, are located inside the bacterial cell (NOT outside, like most pathogens). The presence of the endoflagelli confers to the Treponema pallidum a marked capacity of so-called "spring" movement; thanks to these particular appendages, the microorganism is able to perform contractions, rotations, circular or "corkscrew" movements. The bacterial wall that covers it is also particularly elastic.
The Treponema pallidum It CANNOT be grown on liquid or solid soils: only specific serological tests can ascertain or not the presence of the bacterium.
Among the virulence factors associated with Treponema pallidum remember:

• hyaluronidase (hydrolytic enzyme): favors the penetration of the bacterium into the host
• fibronectin (dimeric glycoprotein): protects the same Treponema pallidum from phagocytosis.
• hemolysins: toxic substances produced by the bacterium

Transmission of infections

Being sensitive to external temperatures, the bacteria of the species Treponema pallidum can only be transmitted by direct contact.
As mentioned above, the Treponema pallidum is the causative agent of syphilis, a widespread venereal disease. In addition to sexual transmission, the Treponema pallidum it can infect the fetus via the placenta during the last stages of pregnancy: in this case, the disease transmitted by the mother and acquired by the unborn child is called "congenital syphilis".

The particular helical structure of Treponema allows it to move even in a viscous medium such as mucus. Arriving later in the blood and lymph, the bacterium infects tissues and mucous membranes.
In some cases, the Treponema pallidum it is transmitted by transfusion of infected blood.
The incubation period for syphilis varies from 2 to 10 weeks.

In-depth study: clinical stages of syphilis

1. primary phase: it is characterized by the presence of syphiloma, a highly contagious lesion that occurs at the injection site, often at the level of the external genitalia. The papule soon evolves into a rigid and painful ulcer. These clinical signs are evident after 3-4 weeks from the infection
2. secondary phase (disseminated syphilis): 6-12 weeks after the disappearance of the primary syphiloma, the second phase of syphilis begins. At this stage, the Treponema pallidum it has spread and replicated in the liver, lymph nodes, joints, muscles, skin and mucous membranes. The characteristic signs of this phase are: widespread papules on the trunk, arms and legs, and skin sores (erosions, erythematous plaques). The affected patient often complains of fever, alopecia, thinning of the eyebrows, headache, loss of appetite. This phase lasts about 8 weeks, after which the patient can enter the latent (asymptomatic) or late (tertiary) phase.
3. tertiary phase: appears many years after the infection, with lesions in the cardiovascular system and CNS, associated with sores on the skin or internal organs.

Infection with Treponema pallidum it is ascertained by means of a sample of fluid extracted from a suspected ulcer. The fluid will subsequently be evaluated under a microscope.
The doctor can also subject the patient to blood tests, looking for any specific antibodies (present in all those affected by syphilis).
Medical statistics show that a large number of syphilis sufferers have a high risk of contracting HIV: for this reason, syphilitics are invited to undergo all necessary tests to test for any concomitant HIV infection.

Prevention and treatment of infections

Since there is no vaccine for syphilis, it is good to refrain from unprotected sex with people at risk; otherwise, regularly carry out blood tests, as well as alert all people with whom you have had high-risk intercourse, up to a year before the onset of symptoms of syphilis.
Infections from Treponema pallidum can be treated with antibiotics such as penicillin (drug of choice), procaine, erythromycin, doxycycline and tetracyclines. Prevention is the best weapon to escape from infections. Treponema pallidum.