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Tuberculosis

Tuberculosis is a common infectious disease caused by mycobacteria tuberculosis, affecting a number of organs, most often the lungs.

Etiology

tuberculosis pathogen
Mycobacterium tuberculosis (large increase).

The causative agent of tuberculosis, mycobacterium, discovered by R. Koch in 1882, belongs to the group of acid-resistant ones. Mycobacterium tuberculosis is a thin rod, often somewhat curved, with slightly rounded ends, with a length of 0.8 to 3-5 microns and a width of 0.2 to 0.5 microns (Fig.).

There are several types of mycobacterium tuberculosis: human, bovine and avian. Recently, atypical mycobacteria have been isolated.

Epidemiology
The main source of infection is people with tuberculosis, secreting mycobacterium tuberculosis with sputum; infection is also possible with the use of products from animals with tuberculosis. The pathogen can be transmitted by airborne droplets, airborne dust, alimentary and contact routes. The incidence and mortality of tuberculosis depends mainly on social factors, the level of development of medical science and health care.

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After the Great October Socialist Revolution, the incidence and mortality from tuberculosis in the USSR as a result of social transformations and special measures began to decline significantly, especially since 1950. There have been significant changes in the nature of tuberculosis lesions found in the diseased. Such rare forms of the disease as miliary tuberculosis, tuberculous meningitis, caseous pneumonia have become extremely rare. Mortality from tuberculosis among children has decreased many times.

mycobacterium tuberculosis
Mycobacterium tuberculosis: 1 - in pure culture; 2 - in culture from a liquid nutrient medium (pronounced arrangement of "braids"); 3 - in the sputum (coloring on the fly); 4 - in the sputum (coloring on Zil - Nelsen); 5 - in the sputum (color by Muhu-Weiss); 6 - in the urine (Spengler staining); 7 - non-acid-resistant mycobacteria and isolated dipteroid sticks; 8 - atypical forms (with cone-shaped bulges and others); 9 - with fluorescence microscopy; 10 - colonies on glycerol-potato medium; 11 - colonies on solid egg medium; 12 - avian type colonies on solid egg medium; 13 - orange culture on solid egg medium.

Pathogenesis and pathological anatomy
It has been established that the penetration of mycobacterium into the human body does not mean the obligatory development of tuberculosis. The body responds to the invasion of mycobacteria by mobilizing defenses, phagocytosis , antibody production, and inflammatory reactions.

Often, mycobacteria remain in the body for a long time without causing specific inflammation. At the same time, macrophage lymphoid cell and plasma cell reaction is observed in lymph nodes as a manifestation of antibody formation in response to the introduction of an antigen (mycobacterium toxin ). However, in violation of the immunological state and the breakdown of the body's defenses, the mycobacterium exhibits its pathogenic effect, and tuberculosis develops as a disease.

From the moment of infection and prior to the development of tuberculosis, it can sometimes take a very long time. In some cases, the disease proceeds against the background of allergy (hyperergy) and unstable immunity, in others there are inverse ratios, or sensitivity to tuberculosis toxin and immunity to tuberculosis remain, as it were, at the same level. All this is reflected in the morphological manifestations of tuberculosis, its clinical course and creates an extraordinary polymorphism, a variety of clinical and morphological manifestations of the disease.

Immunity and Allergies
Immunity in tuberculosis is relative, non-sterile and is supported by the presence of viable, but less virulent bacteria in the body. When infected and the disease changes the body 's reactivity , especially in children. Hypersensitivity of the body - allergy - determines the development of the disease, and in favorable cases, gradually gives way to immunity, which is the basis of further cure.

Tuberculin diagnosis . To identify allergies used intracutaneous Mantoux test and skin test Pirke. For the production of tuberculin samples, ready-to-use ampullated PPD solutions (dry, purified tuberculin-glycerol extract of mycobacterium broth culture) with an activity of 5 tuberculin units (5 TE) in 0.1 ml are released. Intradermal administration of tuberculin (see) is performed on the outer surface of the upper third of the right shoulder (after pre-treating the skin with 70% alcohol) with a special tuberculin or one-gram syringe . The skin of the shoulder is fixed with the left hand so that it is stretched, then a short thin needle is inserted into the skin thickness parallel to its surface, i.e. strictly intradermally. At the same time the needle section and graduation of the syringe should be turned upwards. Inject 0.1 ml of PPD; With the correct technique of conducting the test, a white papule 5–8 mm in diameter is formed in the skin. Checking the reaction in the Mantoux test is performed in 48-72 hours and is considered positive if there is an infiltrate of at least 5 mm in diameter. Hyperemia surrounding infiltration is not taken into account.

When placing the sample, Pirka applies a drop of PPD solution to the skin of the forearm cleaned with 70% alcohol and in its place a notch-scarification of the skin is made with a smallpox feather, after which it is allowed to dry. The reaction should be considered positive in the presence of an infiltrate not less than 5 mm in the direction transverse to the skin incision (Fig. 1-3).

Pierre skin tuberculin test
Fig. 1-3. Pirke skin tuberculin test. Fig. 1. Negative. Fig. 2. Moderately pronounced. Fig. 3. Pronounced.

Positive and positive reactions confirm the presence of sensitization , and a negative tuberculin reaction may indicate the absence of the disease or a cure. In the case of a serious illness, a negative tuberculin reaction may indicate a depletion of the body's defenses.