Tuberculin microbiology. Pathogens of tuberculosis

Pathogenicity factors.

Lipid cord factor– glycolipid, is an adhesion factor, destroys mitochondria of cells of an infected organism,

disrupts their respiratory function and inhibits the migration of polymorphonuclear leukocytes. When cultivated, it causes glueing of vi-

rolled individuals in the form of braids, strands. Tuberculin(tuberculoproteins) has an allergenic effect and causes the development of PCZT.

Glycolipids outer layer of the cell wall ( mycosides) And mannose receptors mycobacteria contribute to unfinished

phagocytosis. Tuberculostearic, phthionic, mycolic and other fatty acids have a toxic effect on tissue.

Siderophores mycobacteria compete with phagocytes for iron; they synthesize iron-containing enzymes and colonize the alveo-

polar macrophages.

Characteristics of the disease

The source of infection is sick people and sick animals (cattle) that secrete mycobacteria. Routes of transmission are often airborne, less often contact and alimentary (milk of cows). Infection is promoted by constant contact and living with a patient with tuberculosis. Pathogenesis of tuberculosis. Inhaled bacteria are phagocytosed by alveolar pulmonary macrophages and transported to regional lymph nodes. Phagocytosis is incomplete. Mycoside glycolipids enhance the toxic effect of the cord factor, damaging mitochondrial membranes and inhibiting phagosomal-lysosomal fusion. The cord factor inhibits the activity of polymorphonuclear phagocytes. At the entrance gate of the lungs in the acini, a primary affect develops, the lymphatic vessels and regional lymph nodes coming from it become inflamed, and primary complex. A granuloma appears in the acini in the form of tubercle. This is facilitated by the accumulation of lactic acid, low pH, and high concentration of carbon dioxide. A large number of lymphoid, plasma cells and fibroblasts accumulate in the granuloma. In the center of the granuloma, areas of cheesy necrosis appear. Here the pathogens are located, around them are epithelioid and giant cells. When immunity is formed, the reproduction of the pathogen slows down and then stops, and PCZT develops. The source of inflammation has subsided

hay, undergoes calcification and fibrosis, calcifications are formed ( Gon's outbreaks). There are no clinical manifestations. There are no phages to gamma interferon, the HLA-dependent presentation of antigens is weakened, the proliferation of T-lymphocytes is inhibited, the complement system is activated along the alternative pathway, and generalization of the infectious process develops. High sensitization of the body leads to toxic-allergic reactions . Clinically, this period is accompanied by cough, hemoptysis, weight loss, sweating, low-grade fever. In persons with immunodeficiency, disseminated (miliary) tuberculosis– granulomas develop in various organs.

Clinical forms of tuberculosis: - focal: affects individual organs (usually in the lungs, bone

system);

- generalized forms: miliary tuberculosis, tuberculous meningitis, tuberculosis of the genitourinary system, intestines and other or-

Immunity has a non-sterile cellular nature. T-lymphocytes are important, releasing mediators that enhance phagocytosis and immunological memory. Antibodies do not inhibit the pathogen. Infectious allergy PCZT develops. There is a high natural resistance to the tuberculosis pathogen.

Laboratory diagnosis of tuberculosis. Differentiation of pathogens of tuberculosis, mycobacteriosis and acid-resistant saprophytes.

Laboratory diagnostics

The materials for the study are sputum, urine, cerebrospinal fluid, lymph node punctate, tissue biopsies. Bacterioscopic method. The smears are stained using the Ziehl-Neelsen method and small red rods are identified. When stained with fluorescent dyes (auramin, rhodamine), mycobacteria give a yellow-white glow in a fluorescent microscope. When the amount of the pathogen is small, enrichment methods are used. Homogenization– the material is treated with alkali, fibrin dissolves and the pathogen is released. Smears are prepared from the centrifugation sediment. Flotation– homogenized sputum is treated with xylene or benzene and shaken thoroughly. Due to its hydrophobicity, the pathogen floats up along with the foam. A smear is prepared from it and stained according to Ziehl-Neelsen. Bacteriological method. The material is treated with sulfuric acid and inoculated on egg media.

For identification M. tuberculosis assess the properties of the pathogen: growth pattern - dry, warty, creamy

colonies (R-form); growth duration – 12-60 days; detect the presence of a cord factor (determined by Price's method- applied to glass

the material being studied is treated with sulfuric acid to destroy acid-sensitive flora and the preparations are immersed in cytosol

military blood, after 3-4 days the preparations are removed, stained according to Ziehl-Neelsen, microscopy shows “braids” of rods, if

due to the cord factor, the pathogen is located amorphously); Mycobacterium tuberculosis is characterized by growth only at a temperature of 37-

380С; they do not grow on plain media or media with salicylates; positive niacin test(medium with chloramine B turns yellow when

accumulation of nicotinic acid); have thermolabile cata lase; reduce nitrates to nitrites; secrete urease; to mi-

Guinea pigs are sensitive to tuberculosis cobacteria. For intraspecific differentiation, phage typing of strains with ten mycobacteriophages is used. To detect hypertension, ELISA or RIF are used, for gene diagnostics, PCR is performed and genetic markers are identified.__ Mycobacterium bovis virulent in S-form; colonies are creamy and smooth; niacin test negative; growth up to 40 days; catalase thermolabile; secrete urease; do not reduce nitrates; growth only at a temperature of 37-400C. Mycobacterum africanum– growth 31-40 days; niacin test is positive; virulent in S-form; catalase is heat labile; do not reduce nitrates; secrete urease. Other properties of kaku M. tuberculosis.Mycobacterium tuberculosis must be differentiated from atypical acid-fast bacteria that cause mycobacteriosis. Atypical acid-fast bacteria have an orange pigment

ment, virulent in the S-form, grow on media with salicylates, have thermostable catalase, growth in 10-20 days at a temperature of 22-450C, no cord factor. Acid-resistant saprophytes M.smegmatis, unlike previous pathogens, grow on simple media, growth duration is 3-4 days, have an S-shape, orange pigment, no signs of pathogenicity, are sensitive to alcohol.

The bioassay is used for erased forms. The test material is rubbed intradermally on guinea pigs. After 10-14 days, an ulcer that does not heal for a long time appears, and the Mantoux reaction becomes positive. Allergy test method is the Mantoux reaction with tuberculin. Intradermal injection tuberculin PPD(PPD– purified protein derivative). If the body is infected (immune), then after 24-48-72 hours infiltration and hyperemia are observed, i.e. PPCT develops. In patients with tuberculosis, the diameter of the papule is 6 mm (or more) larger than in those vaccinated. Gene diagnostics - PCR. Serological method: used to detect antibodies

Morphology of Mycobacterium tuberculosis (red rods) in sputum. Ziehl-Neelsen staining. Gram-positive thin straight or slightly curved rods; - The cell wall contains a large amount of waxes and lipids (mycolic acid), which determines hydrophobicity, resistance to acids, alkalis, and alcohols; - Stained according to Ziehl-Neelsen; - Motile, does not form spores or capsules; - Can be converted to filterable and L-forms

Cultural properties Aerobes; Grow on media containing eggs, glycerin, potatoes, asparagine, vitamins, salts; The most commonly used are Lowenstein-Jensen egg medium and Soton synthetic medium; grow slowly (growth is detected after 2-3 weeks and later); Colonies are dry, wrinkled, grayish; They have biochemical activity that makes it possible to differentiate species. The main test is the niacin test (accumulation of nicotinic acid in a liquid medium. Lowenstein-Jensen medium and the growth of mycobacteria.

Pathogenicity factors Adhesion factor - cord - factor = ester of trehalose and diresidues of mycolic acid; Antiphagocytic factors - waxes (especially wax D), sulfates and some other compounds that prevent the fusion of phago- and lysosomes; Sulfolipids inhibit the activity of lysosomal enzymes; Fosatide and wax fractions of lipids cause sensitization of the body; Acetone-soluble lipids enhance the immunosuppressive properties of mycobacteria and modify host cell membranes; Lipids provide resistance to complement and free radicals of phagocytes. The main factor, tuberculin, has toxic and allergic properties

The interaction of Mycobacterium tuberculosis with the human body begins when the pathogen enters the lungs. After adhesion with the help of a cord factor, they are captured by alveolar macrophages; The events that occur next (macrophages either restrain the proliferation of mycobacteria or not) are determined by the relationship between the bactericidal activity of macrophages and the virulence of mycobacteria. After multiplication inside the macrophage, mycobacteria destroy it. Monocytes, emerging from the bloodstream under the influence of chemotaxis factors, capture mycobacteria released from destroyed macrophages. Macrophages transfer mycobacteria to the nearest lymph nodes, where they persist for a long time due to incomplete phagocytosis. Thus, the initial entry of the pathogen into the lungs or other organs causes development of minor or nonspecific inflammation with macrophage infiltration

Pathogenesis (continued) 2-4 weeks after infection, the next stage of interaction between mycobacteria and the macroorganism begins. In this case, two processes are observed - a reaction of tissue damage like HRT (specific inflammatory reaction) and a reaction of activation of macrophages. With the development of immunity and the accumulation of a large number of activated macrophages in the primary focus, a tuberculous granuloma is formed. Granuloma Granulomas consist of lymphocytes and activated macrophages, that is, epithelioid and giant cells. Epithelioid giant cells The development of a tissue damage reaction leads to the formation of a focus of caseous necrosis in the center of the granuloma. In case of healing of the lesion, necrotic masses become denser, calcified as a result of the deposition of calcium salts, a connective tissue capsule is formed around the lesion - Gon's lesion, but mycobacteria in the form of L-forms retain viability in such a lesion long years With a decrease in the resistance of the macroorganism, activation of the focus occurs with the development of secondary tuberculosis

Immunity Anti-tuberculosis immunity is formed in response to the penetration of mycobacteria into the body during infection or after vaccination and is non-sterile, infectious in nature, which is due to the long-term persistence of L-forms. The decisive role belongs to cellular immunity. The outcome of the disease is determined by the activity of T-helpers, which activate the phagocytic activity of macrophages and T-killer activity

Epidemiology The main source of infection is a patient with respiratory tuberculosis. Transmission routes are airborne, less often alimentary, contact Mycobacterium tuberculosis is very stable in the external environment. In running water they can remain viable for up to 1 year, in soil and manure for 6 months, on various objects for up to 3 months, in library dust for 18 months, in dried pus and sputum for up to 10 months. When boiled, Koch's bacillus dies after 5 minutes, in gastric juice after 6 hours, when pasteurized after 30 minutes, direct sunlight kills mycobacteria within an hour and a half, and ultraviolet rays within 2-3 minutes. Disinfectants containing chlorine kill mycobacteria within 5 hours.

Epidemiology (continued) Tuberculosis is widespread The incidence rate is increasing due to socio-economic factors (the main factor is starvation) Since 1990, a sharp rise in incidence has been recorded worldwide Human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome have caused a marked increase in the number of cases of tuberculosis in some countries On the other hand, the problem is the spread of multidrug-resistant mycobacteria

Treatment Currently, according to the degree of effectiveness, anti-tuberculosis drugs are divided into 3 groups: Group A - isoniazid, rifampicin and their derivatives (rifabutin, rifater) Group B - streptomycin, kanamycin, ethionamide, cycloserine, fluoroquinolones, etc. Group C - PAS and thioacetozone

BCG vaccine (BCG - bacillus Calmette and Guerin) - contains live avirulent mycobacteria obtained from M. bovis through long-term passages on media containing bile Post-vaccination immunity is associated with the formation of hypersensitivity hypersensitivity (delayed type hypersensitivity) Specific prevention

Laboratory diagnostics Clinical material: pus, sputum, blood, bronchial exudate, cerebrospinal fluid, pleural fluid, urine, etc. Methods: 1. Bacterioscopic: direct staining of a sputum smear using the Ziehl-Neelsen method or a smear after enrichment (concentration by flotation or homogenization methods)

Laboratory diagnostics 4. The bacteriological (culture) method is used to test the effectiveness of treatment (2-8 weeks are necessary for the growth of colonies on Lowenstein-Jensen medium and some more time to assess the effect of drugs introduced into the growth medium); 5. Serological method (RSK, ELISA, radioimmune, etc.); 6.Biological method (infection of guinea pigs and rabbits with subsequent isolation of a pure culture of the pathogen); 7. Mantoux tuberculin test (see below); 8.Molecular genetic method (PCR)

Mantoux skin allergy test Intradermal administration of highly purified tuberculin (PPD = Purified Protein Derivative) causes a local inflammatory reaction in the form of infiltration and redness (HRT reaction) in people infected with mycobacteria. Uninfected people do not show any reaction to the introduction of tuberculin. This test is used to identify infected, sensitized people.

Russia is on the list of countries where the largest number of people fall ill and die from tuberculosis every year.

At the same time, in developed countries of the world, phthisiology is a therapeutic area and it is very difficult to find highly specialized specialists who would treat tuberculosis exclusively.

Why is this happening? What microorganism is the causative agent of tuberculosis? And why is there no lasting lifelong immunity against this terrible disease and why do you need to be vaccinated several times?

How to protect yourself from these dangerous microbacteria? We will talk about all this today.

Let's say a few words about the disease itself. Tuberculosis is a disease that is classified as infectious.

The disease affects not only humans, but also animals. This disease is always clinically realized, has a genetic predisposition and depends on factors environment.

As a rule, tuberculosis affects the lungs, but other organs and systems can also be affected (lymph nodes, intestines, bones, kidneys, reproductive organs, central nervous system, etc.).

As the disease develops, characteristic granulomas appear; these are small grains that look like tubercles and nodules.

In ancient times, tuberculosis was called “consumption.” And only in 1882 Heinrich Koch (German microbiologist) was able to discover the causative agent of the disease and remove it in a serum medium.

For his research in 1905, the scientist received the Nobel Prize. What other microorganisms cause tuberculosis?

Microbiology has found the answer to this question. The causative agents of tuberculosis are specific mycobacteria that belong to the group Mycobacterium tuberculosis complex (M. tuberculosis and other closely related species.

In total, the scientific world knows more than 150 species of such bacteria. This microorganism is traditionally called “Koch’s bacillus” in honor of the famous German scientist who discovered this bacterium to the scientific world.

In humans, tuberculosis can be caused by one of three types of mycobacteria:

1. "Koch's stick", in Latin called M. Tuberculоsis. This microorganism causes about 92% of all cases of the disease.
2. Bovine species, M. bovis. This tuberculosis pathogen occurs in 5% of cases.
3. An intermediate type, M. africanum, which most often affects residents of South Africa and occurs in 3% of cases.

It is very rare that you can become infected with tuberculosis from mycobacteria of the avian or mouse type, which are very rare and more common in people infected with immunodeficiency.

Routes of infection

Tuberculosis can be contracted in different ways:

1. By airborne droplets. This option is the most common and affects about 92% of all cases.
2. Through contaminated food (3-4%).
3. From animal to human (about 3%).

All other cases are quite rare. Many of the 150 known species of mycobacteria are safe for humans, while others, on the contrary, are considered conditionally pathogenic.

In other words, they trigger the onset of disease under certain conditions. immune system.

For example, there are so-called mycobacteriosis of the non-tuberculosis type, which includes leprosy. This is a terrible disease. This also includes ulcers, skin infections and more.

If you look under a microscope, tuberculous mycobacteria look like oval rods, slightly rounded at the end.

However, curved and oval shapes are also found. All types of tuberculous mycobacteria, without exception, are resistant to acids, alkalis and alcohol. They are immobile and do not form capsules or spores.

Scientists have established the similarity of Mycobacterium tuberculosis with radiant fungi. What they had in common was:

• slow development in elective environments;
• method of reproduction;
• polymorphism;
• the ability in some cases to form filamentous forms similar to actinomycete fungi.

It is these similarities that have led modern medicine to replace the name “Koch bacteria” with Mycobacterium tuberculosis. The microorganism reproduces by division.

This happens within 24 hours. But they are invulnerable in the following cases:

• able to adapt to any medicines and have genetic memory, which is passed on to “descendants”;
• are not afraid of drying out;
• resistant to most antiseptics;
• feel great in humid environments and water.

In simple terms, mycobacteria are very dangerous microorganisms that can adapt to almost any environmental conditions.

The physiological feature of bacteria is that they are able to synthesize almost all organic compounds for their life activity from any atoms.

This is why the bacillus is so persistent and dangerous to human life.

Let's talk about the bacterial component and the habitat of microorganisms. Mycobacterium tuberculosis is very sensitive to direct sunlight.

So, in hot weather, in the sputum in which infections live, they can die within two hours.

They are especially sensitive to ultraviolet light. Mycobacteria also die when heated.

At 60 degrees and a humid environment they will die within an hour, at 65 degrees - within 15 minutes, at 80 degrees - within 5 minutes.

Interestingly, in fresh, unboiled milk, such bacteria can live for 10 days, and in butter or hard cheeses a few months. Such microorganisms are more resistant to most disinfectants.

Thus, a five percent solution of phenol with 10% Lysol can destroy bacilli within 24 hours! And formalin solution - after 12 hours.

The stick is freeze resistant. IN wastewater it can live for about a year, in manure - up to 10 years. Even in a completely dried state, it can be viable for 3 years!

Without going into the most complex biochemical processes occurring during the metabolism of mycobacteria, we can briefly note the following: the cells of tuberculosis bacteria are very flexible, changeable and resistant to various changes in the environment.

Under certain conditions, they can live for several years, “waiting” for prey! That is why sometimes it is not enough just to be vaccinated against this disease on time.

What anti-tuberculosis prophylactic agents should be used then?

How to avoid contact with mycobacteria?

It is immediately worth noting that in our country it is almost impossible not to encounter pathogenic microorganisms that cause tuberculosis.

That is why infants are vaccinated against tuberculosis immediately after birth to reduce the risk of contact with mycobacteria.

Breast milk, timely vaccinations against tuberculosis, an annual Mantoux test for children - this is not always enough to prevent infection. What measures are still needed?

Oddly enough, but anti-tuberculosis or preventive measures can be considered instilling in children a love of sports, a healthy lifestyle, proper nutrition according to age characteristics, hardening, ventilation of premises and wet cleaning in in public places and so on.

These are the main factors that contribute to a decrease in immunity and increase the possibility of contracting tuberculosis:

• malnutrition (lack of protein in the diet);
• the presence of chronic diseases such as alcoholism, drug addiction, diabetes, etc.;
• mental trauma;
• old age, etc.

We can say that tuberculosis is not just a complex disease, but also a social phenomenon, which, in fact, is a kind of indicator of how well the population of a particular country lives, how treatment and prevention of the disease is organized.

It is impossible to say for sure whether a person will become infected with tuberculosis or not if he does not have constant contact with the patient.

Much here also depends on the state of the immune system, lifestyle, type of mycobacteria and the presence of the environment in which the microbe will be located.

Many people have been carriers of the infection for years without getting sick themselves. For a weakened body, sometimes one contact with a sick person is enough to become infected.

Therefore, try to avoid contact with infected people, lead an active lifestyle and ventilate the premises more often.

Tuberculosis is a chronic human disease, accompanied by damage to the respiratory system, lymph nodes, intestines, bones and joints, eyes, skin, kidneys and urinary tract, genitals, and central nervous system.

The disease is caused by 3 types of mycobacteria: Mycobacterium tuberculosis - human species, Mycobacterium bovis - bovine species, Mycobacterium africanum - intermediate species.

Division Firmicutes, genus Mycobacterium. The generic characteristic is acid, alcohol and alkali resistance.

Morphology, tinctorial and cultural properties

It is a typical representative of the Mycobacterium genus and has the greatest acid resistance. In smears from sputum or organs, mycobacteria are small thin rods measuring 1.5-4×0.4 microns, gram-positive. On artificial nutrient media they can form branching forms. Mycobacterium tuberculosis is highly polymorphic: rod-shaped, granular, filamentous, coccal, filterable and L-forms are found. As a result of variability, acid-yielding forms appear, among which so-called Mukha grains are often found.

Pronounced polymorphism. They have the form of long, thin (M. tuberculosis) or short, thick (M. bovis), straight or slightly curved rods with homogeneous or granular cytoplasm; gram-positive, nonmotile, do not form spores, have a microcapsule. To identify them, Ziehl-Neelsen staining is used. Mycobacteria can form various morphovars (L-forms of bacteria), which persist in the body for a long time and induce anti-tuberculosis immunity.

The causative agents of tuberculosis are characterized by slow growth and are demanding of nutrient media. M. tuberculosis They are aerobic and glycerol dependent. On liquid nutrient media they grow in the form of a dry, cream-colored film. During intracellular development, as well as during growth in liquid media, a characteristic cord factor is revealed, due to which mycobacteria grow in the form of “bundles”. On dense media, growth occurs in the form of a creamy, dry scaly coating with jagged edges (R-form). As the colonies grow, they take on a warty appearance. Under the influence of antibacterial agents, pathogens change cultural properties, forming smooth colonies (S-forms). M.bovis-grow on media more slowly than M. tuberculosis, are pyruvate dependent; on solid nutrient media they form small spherical, grayish-white colonies (S-forms).

High catalase and peroxidase activity. Catalase is thermolabile. M. tuberculosis synthesizes niacin (nicotinic acid) in large quantities, which accumulates in the culture medium and is determined in the Konno test.

Chemical composition: The main chemical components of mycobacteria are proteins, carbohydrates and lipids. Lipids (phosphatides, cord factor, tuberculostearic acid) - cause resistance to acids, alcohols and alkalis, prevent phagocytosis, disrupt the permeability of lysosomes, cause the development of specific granulomas, and destroy cell mitochondria. Mycobacteria induce the development of type IV hypersensitivity reaction (tuberculin).

Pathogenicity factors: o The main pathogenic properties are due to the direct or immunologically mediated action of lipids and lipid-containing structures.

Antigenic structure: During the course of the disease, antiprotein, antiphosphatidic and antipolysaccharide antibodies are formed to antigens, indicating the activity of the process.

The presence of lipids makes them resistant to adverse factors. Drying has little effect. They die when boiled.

The main source of infection is a person suffering from respiratory tuberculosis, who releases microbes into the environment with sputum. The main routes of transmission of infection are airborne droplets and airborne dust.

Mycobacterium tuberculosis remains viable for a long time outside the human or animal body. They live in dried sputum for up to 10 months. Maintain a temperature of 70°C for 20 minutes, and boiling for 5 minutes; in a 5% solution of carbolic acid and a solution of sublimate 1: 1000 they die within a day, in a 2% solution of Lysol - after an hour. Of the disinfectants, the most sensitive are bleach and chloramine.

Pathogenesis and clinic

Pathogenicity factors. Mycobacterium tuberculosis contains endotoxin. Virulent strains include a special lipid called cord factor. The virulence of microbes is also associated with the presence of phthionic and mycolic acids, as well as the polysaccharide-mycolic complex. Koch obtained from tuberculosis bacteria poisonous substance protein nature - tuberculin, the pathogenic effect of which manifests itself only in the infected organism. Tuberculin has the properties of an allergen and is currently used in allergy tests to determine whether humans or animals are infected with mycobacteria. There are several tuberculin preparations. “Old” Koch tuberculin (alt-tuberculin) is the filtrate of a 5-6 week culture of microbacteria killed by heat, grown in glycerin broth. “New” Koch tuberculin is dried mycobacterium tuberculosis, crushed in 5% glycerol to a homogeneous mass. Tuberculin is obtained from bovine mycobacteria. There are also tuberculin preparations purified from ballast substances (PPD, RT).

Various immunodeficiencies contribute to the occurrence of the disease. The incubation period ranges from 3-8 weeks. up to 1 year or more. In the development of the disease, primary, disseminated and secondary tuberculosis are distinguished, which is the result of endogenous reactivation of old foci. In the zone of penetration of mycobacteria, a primary tuberculosis complex arises, consisting of an inflammatory focus, affected regional lymph nodes and altered lymphatic vessels between them. Dissemination of microbes can occur broncho-, lympho- and hematogenously. The specific inflammation in tuberculosis is based on a type IV hypersensitivity reaction, which prevents the spread of microbes throughout the body.

There are pulmonary and extrapulmonary clinical forms of tuberculosis, which affect bones, joints, skin, kidneys, larynx, intestines and other organs.
There are usually periods of improvement and deterioration; the final result is determined by the state of the macroorganism. The disease can develop acutely, but more often it occurs chronically, over many years. Weakness, night sweats, fatigue, loss of appetite, slight rises in temperature in the evening, and cough are noted. Fluoroscopy of the lungs reveals darkening of varying degrees: focal or diffuse.

Anti-tuberculosis immunity is non-sterile infectious, due to the presence of L-forms of mycobacteria in the body.

Diagnosis is carried out using bacterioscopy, bacteriological examination and biological testing. All methods are aimed at detecting mycobacteria in pathological material: sputum, bronchial washings, pleural and cerebral fluids, pieces of tissue from organs.

Mandatory examination methods include bacterioscopic, bacteriological examination, biological test, tuberculin diagnostics, based on determining the body's increased sensitivity to tuberculin. More often, to detect infection and allergic reactions, an intradermal Mantoux test is performed with purified tuberculin in a standard dilution. For rapid diagnosis of tuberculosis, RIF (immunofluorescence reaction) and PCR (polymerase chain reaction) are used. . For mass screening of the population and early detection of active forms of tuberculosis, you can use ELISA (enzyme-linked immunosorbent assay), aimed at detecting specific antibodies.

Microbiological diagnostics includes microscopic, microbiological, biological and serological methods. Microscopy is the most common method. It is simple, accessible, and allows you to quickly get an answer. During microscopy of sputum, purulent dense particles are selected and carefully rubbed into a thin layer between two glass slides. Air-dried, flame-fixed and Ziehl-Neelsen stained. Mycobacterium tuberculosis is thin, slightly curved rods, painted bright red; the rest of the background of the preparation is blue. The disadvantage of the method is its low sensitivity. Increasing the sensitivity of microscopy in diagnosing tuberculosis is achieved using enrichment methods. One of them is the homogenization of the material by exposing it to various substances that dissolve mucus (alkali, antiformin). Then the material under study is centrifuged, a smear is prepared from the sediment and examined under a microscope.

The flotation (floating) method is more effective, based on the fact that after prolonged shaking of the test material homogenized with caustic soda with distilled water and xylene (or benzene), a layer of foam is formed that floats to the top and captures mycobacterium tuberculosis. The foam layer is removed and layered onto a warm glass slide several times as it dries. This increases the possibility of detecting Mycobacterium tuberculosis.

Fluorescence microscopy is more sensitive than conventional microscopy. The preparation is prepared as usual, fixed with Nikiforov’s mixture and stained with auramine at a dilution of 1: 1000. Then the preparation is bleached with hydrochloric acid and stained with acid fuchsin, which “extinguishes” the glow of the leukocytes, mucus and tissue elements in the preparations, creating a contrast between the dark background and the luminous ones bright golden-green light mycobacterium tuberculosis. The preparation is examined under a fluorescent microscope. The disadvantage of microscopy is the possibility of errors in the presence of acid-resistant saprophytes.

If the result of microscopic examination is negative, microbiological and biological methods are used. The test material is pre-treated with a 6% sulfuric acid solution to destroy foreign microflora.

The microbiological method makes it possible to identify 20-100 mycobacteria in the studied material. Acid-resistant saprophytes are differentiated from Mycobacterium tuberculosis by cultural characteristics (growth of saprophytes is possible at room temperature for several days). The disadvantage of this method is the slow growth of mycobacterium tuberculosis on nutrient media (the crops are kept in a thermostat for 2-3 months).

Accelerated methods for isolating cultures of Mycobacterium tuberculosis have been developed - Price and Shkolnikova. The essence of these methods is that the material under study is applied to a glass slide, treated with sulfuric acid, washed with an isotonic sodium chloride solution and placed in a nutrient medium with citrated blood. After 5-7 days, the glass is removed and examined according to the Ziehl-Nielsen test. Microscopy at low magnification. Microcolonies of virulent strains of mycobacteria have the form of ropes or braids.

When using the biological method, the processed pathological material is injected into the groin area of ​​guinea pigs. Even in the presence of single tuberculosis mycobacteria, the animal becomes ill: after 6-10 days, the regional lymph nodes enlarge, and a large number of tuberculosis mycobacteria are found in them. After 3-6 weeks the animal dies from a generalized tuberculosis infection.

To determine whether the body is infected with mycobacteria, the allergic method is used. An intradermal test with tuberculin (Mantoux reaction) and a Pirquet skin test are used. In those infected with mycobacteria, redness and swelling form at the site of tuberculin injection.

According to the degree of effectiveness, anti-tuberculosis drugs are divided into groups: group A - isoniazid, rifampicin; group B - pyrazinamide, streptomycin, florimycin; group C – PAS, thioacetozone. In the presence of concomitant microflora and multidrug resistance of mycobacteria, fluoroquinolones and aldozone are used.

Specific prevention is carried out by administering a live vaccine - BCG (BCG), intradermally on the 2-5th day after the birth of the child. Subsequent revaccinations are carried out. A Mantoux test is first performed to identify tuberculin-negative individuals subject to revaccination.

Opportunistic mycobacteria: family Mycobacteriaceae, genus Mycobacterium. Similar in biological properties, but resistant to anti-tuberculosis drugs.

Mycobacteria

The genus Mycobacterium (family Mycobacteriaceae, order Actinomycetales) includes more than 100 species that are widespread in nature. Most of them are saprophytes and opportunistic pathogens. In humans they cause tuberculosis (Mycobacterium tuberculosis - in 92% of cases, Mycobacterium bovis - 5%, Mycobacterium africanus - 3%) and leprosy (Mycobacterium leprae).

Mycobacterium tuberculosis.

Mycobacterium tuberculosis, the main causative agent of tuberculosis in humans, was discovered in 1882 by R. Koch.

Tuberculosis (tuberculosis, phthisis) is a chronic infectious disease. Depending on the location of the pathological process, tuberculosis of the respiratory system and extrapulmonary forms are distinguished (tuberculosis of the skin, bones and joints, kidneys, etc.). The localization of the process to a certain extent depends on the routes of penetration of mycobacteria into the human body and the type of pathogen.

Morphology, physiology. Mycobacterium tuberculosis are gram-positive straight or slightly curved rods 1-4 x 0.3-0.4 µm. The high lipid content (40%) gives the cells of Mycobacterium tuberculosis a number of characteristic properties: resistance to acids, alkalis and alcohol, difficult perception of aniline dyes (the Ziehl-Neelsen method is used to stain tuberculosis bacilli, using this method they are painted pink). There cannot be other acid-fast microorganisms in the sputum, so their detection is an indication of possible tuberculosis. In crops there are granular forms, branching, Mukha grains - spherical, acid-compliant, easily stained by Gram (+). Transition to filterable and L-forms is possible. They are immobile, do not form spores or capsules.

To propagate Mycobacterium tuberculosis in laboratory conditions, complex nutrient media containing eggs, glycerin, potatoes, and vitamins are used. Stimulate the growth of mycobacteria aspartic acid, ammonium salts, albumin, glucose, Tween-80. The most commonly used are Lowenstein-Jensen medium (egg medium with the addition of potato flour, glycerin and salt) and Soton synthetic medium (contains asparagine, glycerin, ferric citrate, potassium phosphate). Mycobacterium tuberculosis multiplies slowly. The generation period is long - cell division in optimal conditions occurs once every 14-15 hours, while most bacteria of other genera divide after 20-30 minutes. The first signs of growth can be detected 8-10 days after sowing. Then (after 3-4 weeks) wrinkled, dry colonies with uneven edges (resembling cauliflower) appear on solid media. In liquid media, a delicate film first forms on the surface, which thickens and falls to the bottom. The medium remains transparent.

They are obligate aerobes (they settle in the apices of the lungs with increased aeration). Bacteriostatins (malachite or brilliant green) or penicillin are added to the media to suppress the growth of accompanying microflora.

Signs that are used to differentiate Mycobacterium tuberculosis from some other mycobacteria found in the materials under study:

growth time during isolation, days.

loss of catalase activity after heating for 30 min at 68°C

Designations: + - presence of a sign, - - absence of a sign, ± - sign is not constant.

Antigens. Mycobacterial cells contain compounds whose protein, polysaccharide and lipid components determine antigenic properties. Antibodies are formed against tuberculin proteins, as well as polysaccharides, phosphatides, and cord factor. The specificity of antibodies to polysaccharides and phosphatides is determined by RSK, RNGA, and gel precipitation. The antigenic composition of M. tuberculosis, M. bovis, M. leprae and other mycobacteria (including many saprophytic species) is similar. Tuberculin protein (tuberculin) has pronounced allergenic properties.

Resistance. Once in the environment, Mycobacterium tuberculosis retains its viability for a long time. Thus, microorganisms survive in dried sputum or dust for several weeks, in wet sputum for 1.5 months, on objects surrounding the patient (linen, books) for more than 3 months, in water for more than a year; in soil – up to 6 months. These microorganisms persist for a long time in dairy products.

Mycobacterium tuberculosis is more resistant to the action of disinfectants than other bacteria; higher concentrations and longer exposure times are required to destroy them (phenol 5% - up to 6 hours). When boiled, they die instantly and are sensitive to direct sunlight.

Ecology, distribution and epidemiology. Tuberculosis affects 12 million people in the world, and another 3 million get sick every year. Under natural conditions, M. tuberculosis causes tuberculosis in humans and great apes. Among laboratory animals, guinea pigs are highly sensitive, and rabbits are less sensitive. Rabbits are highly sensitive to M. bovis, the causative agent of tuberculosis in cattle, pigs and humans, and guinea pigs are less sensitive. M. africanus causes tuberculosis in humans in tropical Africa.

The source of infection for tuberculosis is people and animals with actively progressing tuberculosis, with the presence of inflammatory and destructive changes, secreting mycobacteria (mainly pulmonary forms). A sick person can infect 18 to 40 people. A single contact is not enough for infection (the main condition is prolonged contact). The degree of susceptibility also matters for infection.

A sick person can secrete from 7 to 10 billion mycobacterium tuberculosis per day. The most common is the airborne route of infection, in which the pathogen enters the body through the upper respiratory tract, sometimes through the mucous membranes of the digestive tract (alimentary route) or through damaged skin.

Pathogenicity. Mycobacteria do not synthesize exo- and endotoxin. Tissue damage is caused by a number of microbial cell substances. Thus, the pathogenicity of tuberculosis pathogens is associated with the direct or immunologically mediated damaging effect of lipids ( wax D, muramine dipeptide, phthionic acids, sulfatides ), which manifests itself when they are destroyed. Their action is expressed in the development of specific granulomas and tissue damage. The toxic effect is exerted by a glycolipid (trehalosodimicolate), the so-called cord factor . It destroys the mitochondria of cells of the infected organism, disrupts respiratory function, and inhibits the migration of leukocytes to the affected area. Mycobacterium tuberculosis in cultures that have a cord factor form tortuous strands.

Pathogenesis of tuberculosis. Tuberculosis is a chronic granulomatous infection that can affect any tissue, most often in children: lungs, lymph nodes, bones, joints, meninges; in adults: lungs, intestines, kidneys.

Primary tuberculosis (children's type) – The infection may last for several weeks. In the zone of penetration and reproduction of mycobacteria, an inflammatory focus occurs (the primary effect is an infectious granuloma), sesitization and a specific inflammatory process are observed in the regional lymph nodes (in case of lung damage - thoracic, pharyngeal lymphoid accumulations, tonsils) - the so-called primary tuberculosis complex is formed (usually the lower lobe of the right lung is affected). Since a state of sensitization develops, reproduction in a sensitized organ leads to specific changes in the tissue: microorganisms are absorbed by macrophages → a barrier (phagosome) is formed around them → lymphocytes attack these cells (lining up along the periphery of the lesion) → specific tubercles (tuberculum - tubercle) are formed – small (diameter 1-3 mm), granular, white or grayish-yellow. Inside are bacteria, then a limiting belt of (giant or epithelioid) cells, then lymphoid cells, then fibroid tissue. Tubercles can merge into conglomerates → compression of blood vessels → circulatory disorders → necrosis in the center of the conglomerate in the form of dry cheese-like crumbs (caseous necrosis). The vessel wall may become necrotic → bleeding.

The resulting tubercle can:

● persist for a long time (not accompanied by clinical manifestations);

● in a benign course of the disease, the primary lesion can resolve, the affected area can scar (the function of the organ is not impaired) or calcify (Gon lesions are formed, which persist for life without clinical manifestations). However, this process does not end with the complete liberation of the organism from the pathogen. In lymph nodes and other organs, tuberculosis bacteria persist for many years, sometimes throughout life. Such people, on the one hand, are immune, but on the other, remain infected.

● Softening and infiltration of the primary lesion may occur → this may be accompanied by a breakthrough of the lesion into nearby tissues → can lead to rupture of the bronchus → necrotic tissue slips into the lumen of the bronchus → a spoon-shaped cavity (caverna) is formed.

If this process occurs in the intestines or on the surface of the skin, a tuberculous ulcer is formed.

Chronic tuberculosis (adult type) occurs as a result of reinfection (usually endogenous). Activation of the primary complex develops as a result of reduced body resistance, which is facilitated by unfavorable living and working conditions (poor nutrition, low insolation and aeration, low mobility), diabetes mellitus, silicosis, pneumoconiosis, physical and mental trauma, other infectious diseases, genetic predisposition. Women are more likely to develop the disease into a chronic form. Activation of the primary tuberculosis complex leads to generalization of the infectious process.

● Most often pulmonary (upper and posterior part of the upper lobe) with the formation of caverns; Staphylococcus and Streptococcus can multiply in the walls of the caverns → debilitating fever; if the walls of blood vessels are eroded → hemoptysis. Scars form. Sometimes there are complications: tuberculous pneumonia (with a sudden spill of exudate from the lesion) and pleurisy (if the damaged areas of the lungs are close to the pleura). Therefore, any pleurisy should be considered a tuberculous process until the contrary is proven.

● The infection can spread hematogenously and lymphogenously.

● Bacteria can spread to nearby tissues.

● They can move along natural pathways (from the kidneys to the ureters).

● Can spread throughout the skin.

● Tuberculous sepsis may develop (material loaded with microorganisms from tubercles enters a large vessel).

Dissemination of pathogens leads to the formation of tuberculosis foci in various organs, prone to decay. Severe intoxication causes severe clinical manifestations of the disease. Generalization leads to damage to the organs of the genitourinary system, bones and joints, meninges, and eyes.

Clinic depends on the location of the lesion, the common ones are prolonged malaise, rapid fatigue, weakness, sweating, weight loss, and subfibrile temperature in the evenings. If the lungs are affected, there is a cough; if the pulmonary vessels are destroyed, there is blood in the sputum.

Immunity. Infection with Mycobacterium tuberculosis does not always lead to the development of the disease. Susceptibility depends on the state of the macroorganism. It increases significantly when a person is in unfavorable conditions that reduce overall resistance (exhausting work, insufficient and poor nutrition, poor living conditions, etc.). A number of endogenous factors also contribute to the development of the tuberculosis process: diabetes mellitus; diseases treated with corticosteroids; mental illnesses accompanied by depression and other diseases that reduce the body's resistance. The significance of antibodies formed in the body in the formation of resistance to tuberculosis infection is still unclear. It is believed that antibodies to Mycobacterium tuberculosis are “witnesses” of immunity and do not have an inhibitory effect on the pathogen.

Cellular immunity is of great importance. The indicators of its changes are adequate to the course of the disease (according to the reaction of blast transformation of lymphocytes, the cytotoxic effect of lymphocytes on “target” cells containing mycobacterial antigens, the severity of the reaction of inhibition of macrophage migration). T-lymphocytes, after contact with mycobacterial antigens, synthesize cellular immunity mediators that enhance the phagocytic activity of macrophages. When the function of T-lymphocytes was suppressed (thymectomy, administration of antilymphocyte sera, other immunosuppressants), the tuberculosis process was fleeting and severe.

Tuberculosis microbacteria are destroyed intracellularly in macrophages. Phagocytosis is one of the mechanisms leading to the liberation of the body from Mycobacterium tuberculosis, but it is often incomplete.

Another important mechanism that helps limit the proliferation of mycobacteria and fix them in foci is the formation of infectious granulomas with the participation of T-lymphocytes, macrophages and other cells. This demonstrates the protective role of HRT.

Immunity in tuberculosis was previously called non-sterile. But not only the preservation of living bacteria that support increased resistance to superinfection is important, but also the phenomenon of “immunological memory”. In tuberculosis, a HRT reaction develops.

Laboratory diagnostics tuberculosis is carried out using bacterioscopic, bacteriological and biological methods. Allergy tests are sometimes used.

Bacteriological method . Mycobacterium tuberculosis is detected in the material under study by microscopy of smears stained according to Ziehl-Neelsen and using luminescent dyes (most often auramine). You can use centrifugation, homogenization, flotation of the material (homogenization of daily sputum → adding xylene (or toluene) to the homogenate → xylene floats, entraining mycobacteria → this film is collected on glass → xylene evaporates → a smear is obtained → staining, microscopy). Bacterioscopy is considered as an indicative method. Accelerated methods are used to detect mycobacteria in crops, for example, using the Price method (microcolonies). Microcolonies also make it possible to see the presence of a cord factor (the main virulence factor), due to which the bacteria that form it form braids, chains, and strands.

Bacteriological method is fundamental in the laboratory diagnosis of tuberculosis. The isolated cultures are identified (differentiated from other types of mycobacteria), and sensitivity to antimicrobial drugs is determined. This method can be used to monitor the effectiveness of treatment.

Serological methods are not used for diagnosis, since there is no correlation between the content of antibodies and the severity of the process. Can be used in research work.

Biological method used in cases where the pathogen is difficult to isolate from the test material (most often when diagnosing renal tuberculosis from urine) and to determine virulence. Material from the patient is used to infect laboratory animals (guinea pigs susceptible to M. tuberculosis, rabbits susceptible to M. bovis). Observation is carried out for 1-2 months until the death of the animal. From the 5-10th day you can examine the punctate of the lymph node.

Allergy tests. To carry out these tests, use tuberculin– a preparation from M. tuberculosis. This substance was first obtained by R. Koch in 1890 from boiled bacteria (“old tuberculin”). Now tuberculin, purified from impurities and standardized in ED (PPD - purified protein derivative), is used. This is a filtrate of heat-killed bacteria, washed with alcohol or ether, and freeze-dried. From an immunological point of view, a hapten reacts with immunoglobulins fixed on T-lymphocytes.

The Mantoux test is performed by intradermal injection of tuberculin. Accounting of results in 48-72 hours. Positive result– local inflammatory reaction in the form of edema, infiltration (hardening) and redness – papula. A positive result indicates sensitization (or the presence of mycobacteria in the body). Sensitization can be caused by infection (the reaction is positive 6-15 weeks after infection), disease, immunization (in those vaccinated with a live vaccine).

A tuberculin test is performed for the purpose of selection for revaccination, as well as to assess the course of the tuberculosis process. The Mantoux turn also matters: positive(after a negative test is positive) – infection, negative(negative after a positive test) – death of mycobacteria.

Prevention and treatment. For specific prevention, a live vaccine is used BCG– BCG (Bacille de Calmette et de Guerin). The BCG strain was obtained by A. Calmette and M. Gerin by long-term passaging of tuberculosis bacilli (M. bovis) on a potato-glycerin medium with the addition of bile. They made 230 subcultures over 13 years and obtained a culture with reduced virulence. In our country, all newborns are currently vaccinated against tuberculosis on the 5-7th day of life using the intradermal method (outer surface of the upper third of the shoulder), after 4-6 weeks an infiltrate is formed - pustula (small scar). Mycobacteria take root and are found in the body from 3 to 11 months. Vaccination protects against infection by wild street strains during the most vulnerable period. Revaccination is carried out for persons with a negative tuberculin test at intervals of 5-7 years until the age of 30 (in grades 1, 5-6, 10 at school). In this way, infectious immunity is created, in which a HRT reaction occurs.

To treat tuberculosis, antibiotics and chemotherapy drugs are used, to which the pathogens are sensitive. These are first-line drugs: tubazid, ftivazide, isoniazid, dihydrostreptomycin, PAS and second-line drugs: ethionamide, cycloserine, kanamycin, rifampicin, viomycin. All anti-tuberculosis drugs act bacteriostatically; resistance to any drug quickly develops (cross-resistance), therefore, for treatment, combination therapy is carried out simultaneously with several drugs with different mechanisms of action, with frequent changes in the combination of drugs.

The complex of therapeutic measures uses desensitizing therapy, as well as stimulation of natural defense mechanisms body.

Mycobacterium leprosy.

The causative agent of leprosy (leprosy) - Mycobacterium leprae was described by G. Hansen in 1874. Leprosy is a chronic infectious disease that occurs only in humans. The disease is characterized by generalization of the process, damage to the skin, mucous membranes, peripheral nerves and internal organs.

Morphology, physiology. Mycobacteria leprae are straight or slightly curved rods with a length of 1 to 7 microns, a diameter of 0.2-0.5 microns. In the affected tissues, microorganisms are located inside the cells, forming dense spherical clusters - leprosy balls, in which the bacteria are closely adjacent to each other with their lateral surfaces (“cigarette sticks”). Acid-resistant, stained red using the Ziehl-Neelsen method.

Mycobacteria leprosy cannot be cultivated on artificial nutrient media. In 1960, an experimental model was created with infection of white mice in the paw pads, and in 1971 - armadillos, in which typical granulomas (lepromas) are formed at the site of injection of mycobacteria leprosy, and with intravenous infection a generalized process develops with the proliferation of mycobacteria in the affected areas. tissues.

Antigens. Two antigens were isolated from leproma extract: a heat-stable polysaccharide (group for mycobacteria) and a heat-labile protein, highly specific for leprosy bacilli.

Ecology and distribution. The natural reservoir and source of the causative agent of leprosy is a sick person. Infection occurs through prolonged and close contact with a sick person.

The properties of the pathogen and its relationship to the effects of various environmental factors have not been sufficiently studied.

Pathogenicity of the pathogen and pathogenesis of leprosy. The incubation period of leprosy is on average 3-5 years, but it can be extended to 20-30 years. The development of the disease occurs slowly over many years. There are several clinical forms, of which the most severe and epidemically dangerous is lepromatous: multiple infiltrates-lepromas are formed on the face, forearms, and legs, which contain a huge number of pathogens. Subsequently, the lepromas disintegrate and slowly healing ulcers form. Skin, mucous membranes, lymph nodes, nerve trunks, and internal organs are affected. The other form, tuberculoid, is clinically milder and less dangerous to others. In this form, the skin is affected, and nerve trunks and internal organs are less common. Skin rashes in the form of small papules are accompanied by anesthesia. There are few pathogens in the lesions.

Immunity. During the development of the disease, sharp changes occur in immunocompetent cells, mainly the T-system - the number and activity of T-lymphocytes decreases and, as a result, the ability to respond to Mycobacterium leprosy antigens is lost. Mitsuda's reaction to the introduction of lepromin into the skin in patients with the lepromatous form, which occurs against the background of deep suppression of cellular immunity, is negative. In healthy individuals and in patients with tuberculoid leprosy, it is positive. This prba, thus, reflects the severity of damage to T-lymphocytes and is used as prognostic, characterizing the effect of treatment. Humoral immunity is not impaired. Antibodies to Mycobacterium leprosy are found in high titers in the blood of patients, but they apparently do not play a protective role.

Laboratory diagnostics. Using the bacterioscopic method, examining scrapings from the affected areas of the skin and mucous membranes, characteristically located mycobacteria of leprosy of a typical shape are detected. Smears are stained according to Ziehl-Neelsen. There are currently no other methods of laboratory diagnosis.

Prevention and treatment. There is no specific prevention of leprosy. A set of preventive measures is carried out by anti-leprosy institutions. Patients with leprosy are treated in leper colonies until clinical recovery, and then on an outpatient basis.

In our country, leprosy is rarely registered. Isolated cases occur only in some areas. According to WHO, there are more than 10 million leprosy patients in the world.

Leprosy is treated with sulfone drugs (diacetylsulfone, selusulfone, etc.). Desensitizing agents, drugs used to treat tuberculosis, as well as biostimulants are also used. Immunotherapy methods are being developed.

Topic 37. Pathogens of tuberculosis

GBOU VPO “Ural State Medical University” of the Ministry of Health Russian Federation Department of Microbiology, Virology and Immunology

Guidelines for practical exercises for students

OOP specialty 060301.65 Pharmacy Discipline C2.B.11 Microbiology

1. Topic: Pathogens of tuberculosis

2. Objectives of the lesson: To study with students the properties of tuberculosis pathogens, pathogenicity factors, pathogenesis, methods of diagnosis, prevention and treatment of tuberculosis.

3. Objectives of the lesson:

3.1. Studying the properties of tuberculosis pathogens.

3.2. Study of the pathogenesis of tuberculosis.

3.3. Study of methods of diagnosis, prevention and treatment of tuberculosis.

3.4. Doing independent work.

drugs according to Tsil-

problems and processes,

and clinical sciences in

willingness to participate

in setting up scientific

work with the population

4. Duration of the lesson in academic hours: 3 hours.

5. Test questions on the topic:

5.1. Morphological, tinctorial, cultural and biochemical properties of tuberculosis pathogens.

5.2. Pathogenicity factors of tuberculosis pathogens.

5.3. Methods of diagnosis, prevention and treatment of tuberculosis.

6. Tasks and guidelines for their implementation.

During the lesson, the student must:

6.1. Answer the teacher's questions.

6.2. Take part in the discussion of the issues being studied.

6.3. Do independent work.

Theoretical background Tuberculosis is a chronic infectious disease accompanied by

specific damage to various organs and systems (respiratory organs, lymph nodes, intestines, bones, joints, eyes, skin, kidneys, urinary tract, genitals, central nervous system). With tuberculosis, specific granulomas (granulum - grain) are formed in organs in the form of nodules or tubercles (tuberculum - tubercle), followed by their curdled degeneration (disintegration) and calcification.

Historical reference. Since ancient times, this disease was known under the names consumption, tubercle, scrofula due to its characteristic clinical signs. Laennec was the first to separate “consumption” from other pulmonary diseases in 1819; he coined the term “tuberculosis” (hence the synonym - tuberculosis). In 1882, R. Koch discovered the causative agent of tuberculosis and obtained a pure culture on a serum medium (Koch's bacillus or bacillus). In 1890, R. Koch obtained tuberculin (“water-glycerol extract of tuberculosis cultures”). In 1911, R. Koch was awarded the Nobel Prize for the discovery of the causative agent of tuberculosis.

Taxonomy. Division Firmicutes, family Mycobacteriaceae, genus Mycobacterium.

Tuberculosis in humans is most often caused by three types of mycobacteria: M. tuberculosis (Koch's bacillus, human species - causes the disease in 92% of cases), M. bovis (bovine species - causes the disease in 5% of cases), M. africanum (intermediate species - causes the disease in 3% of cases, much more often in South Africa). Rarely, tuberculosis in humans is caused by M. microti (mouse type) and M. avium (avian type, causing infection in immunocompromised individuals).

Morphological and tinctorial properties. The causative agents of tuberculosis are characterized by pronounced polymorphism (coccoid, filamentous, branched, flask-shaped forms). They mainly have the form of long thin (M. tuberculosis, M. africanum) or short and thick (M. bovis) rods with granular cytoplasm containing from 2 to 12 grains of various sizes (metaphosphate grains - Mukha grains). Sometimes they form thread-like structures reminiscent of fungal mycelium, which is the basis for their name (mykes - fungus and bacterium - bacterium). Fixed. There is no dispute. They have a microcapsule.

Gram-positive. Mycobacteria are acid-, alcohol- and alkali-resistant bacteria. For their coloring, the Tsil- method is used.

Nielsen (thermal acid etching with carbol fuchsin). With this color, mycobacteria look like bright red rods, located singly or in small clusters of 2-3 cells.

Cultural properties. Obligate aerobes. They grow slowly due to the presence of lipids in the cell wall, which slow down the metabolism with the environment. The optimal growth temperature is 37-38ºС. The optimal pH value is 6.8-7.2. Mycobacteria are demanding on nutrient media and are glycerol-dependent. To suppress the toxic effect of fatty acids formed during metabolism, activated carbon, animal blood serum and albumin are added to the media, and to suppress the growth of accompanying microflora, dyes (malachite green) and antibiotics that do not act on mycobacteria are added.

Selective nutrient media for mycobacteria:

— Levenshtein-Jensen, Finn-2 egg media;

— Middlebrook glycerol media;

- potato media with bile;

— Shkolnikova’s semi-synthetic medium;

- synthetic media Soton, Dubos.

On solid media, on days 15-20 of incubation, mycobacteria form rough, dense, cream-colored, warty-looking colonies (reminiscent

In liquid media, after 5-7 days a thick, dry, wrinkled, cream-colored film forms on the surface. At the same time, the broth remains transparent.

For express diagnostics, the method of microcultivation on glasses in a liquid medium (Price microculture method) is used, in which after 48-72 hours the growth of mycobacteria is observed in the form of intertwined girlish “braids” or “harnesses” due to the cord factor (English cord - tourniquet, rope).

Chemical composition. The main components of mycobacteria: proteins (tuberculoproteins), carbohydrates and lipids.

Tuberculoproteins make up 56% of the dry mass of microbial cell matter. They are the main carriers of the antigenic properties of mycobacteria, are highly toxic, and cause the development of type 4 hypersensitivity reactions.

Polysaccharides account for 15% of the dry mass of mycobacterial matter. These are genus-specific haptens.

The share of lipids (phthionic acid, butyric, palmitic, tuberculostearic and other fatty acids, cord factor and wax D, which includes mycolic acid) accounts for 10 to 40% of the dry mass of the mycobacterial substance. The high lipid content determines the pathogen's acid, alcohol, and alkali resistance, virulence, difficulty in staining cells using conventional methods, and stability in the environment. Lipids shield the bacterial cell, suppress phagocytosis, block the activity of cellular enzymes, and cause the development of granulomas and caseous necrosis.

Resistance. In the dried sputum of a patient, the cells remain viable and virulent for 5-6 months. They remain on the patient's items for more than 3 months. They remain in soil for up to 6 months, in water for up to 15 months. Sunlight causes the death of mycobacteria in 1.5 hours, UFL – in 2-3 minutes. During pasteurization they die within 30 minutes. Chlorine-containing

the drugs cause the death of tuberculosis pathogens within 3-5 hours, 5% phenol solution - after 6 hours.

Factors of pathogenicity of mycobacteria:

- cord factor - a glycolipid of the cell wall, causes damage to cell membranes and inhibits the formation of phagolysosomes, causing the development of incomplete phagocytosis;

The causative agents of tuberculosis do not produce exotoxins. Cell breakdown products are highly toxic.

The main factor in the pathogenicity of mycobacteria is the cord factor (the name comes from the English cord - tourniquet, rope). The cord factor determines the “crowded type of growth” in liquid media in the form of “twisting strands” (or braids), in which mycobacterial cells are arranged in parallel chains.

Epidemiology. Tuberculosis is widespread. The main source of infection is a sick person with respiratory tuberculosis, who releases microbes into the environment with sputum. Sources of infection can also be people with extrapulmonary forms of tuberculosis and sick animals (cattle, camels, pigs, goats and sheep). The main mechanism of infection is aerogenic. The routes of transmission of the pathogen are airborne droplets and airborne dust. Entrance gate this includes the mucous membrane of the oral cavity, bronchi and lungs. Less commonly, infection with tuberculosis can occur through the alimentary (food) route through consumption of thermally unprocessed meat and dairy products. Contact-household transmission of infection from tuberculosis patients through the use of infected clothing, toys, books, dishes and other items is possible. There are known cases of human infection while caring for sick animals.

Pathogenesis. Having penetrated the human body, mycobacteria are phagocytosed.

Phagosomes are formed in phagocytes, inside which mycobacteria remain alive and multiply. In phagocytes, mycobacteria are transported to regional lymph nodes, remaining for a long time in a “dormant” state (incomplete phagocytosis). In this case, inflammation of the lymphatic tract (lymphangitis) and lymph nodes (lymphadenitis) occurs. At the site of pathogen penetration, a focus of inflammation is formed. Over the course of several weeks, this inflammation becomes specific (a delayed-type hypersensitivity reaction develops), resulting in the formation of a granuloma. Subsequently, the transformation of macrophages into epithelioid cells occurs. When epithelioid cells fuse, giant multinucleated cells are formed. A connective tissue capsule is formed around the source of inflammation, and necrotic tissues become calcified. As a result of this, the formation of a primary tuberculosis complex occurs, inside which there is caseous necrotic tissue and live mycobacteria remain.

Clinic. The incubation period lasts from 3-8 weeks to 1 year or more.

The clinical manifestations of tuberculosis are diverse, since mycobacteria can affect any organs (intestines, genitourinary organs, skin, joints). Symptoms of tuberculosis are fatigue, weakness, weight loss

body, prolonged low-grade fever, profuse night sweats, cough with bloody sputum, shortness of breath. There are no symptoms unique to tuberculosis. When the skin is damaged, ulcerated lesions are observed. With tuberculosis of bones and joints, lesions occur that are characteristic of arthritis of any etiology: thinning of cartilage, the appearance of spines, narrowing of joint cavities.

Immunity. Anti-tuberculosis immunity is formed in response to the penetration of mycobacteria into the body during infection or vaccination and is non-sterile in nature, which is due to the long-term persistence of bacteria in the body. It manifests itself 4-8 weeks after microbes enter the body. Both cellular and humoral immunity are formed.

Cellular immunity is manifested by a state of hypersensitivity (sensitization). Thanks to this, the body acquires the ability to quickly bind a new dose of the pathogen and remove it from the body: T-lymphocytes recognize cells infected with mycobacteria, attack them and destroy them.

Humoral immunity is manifested by the synthesis of antibodies to mycobacterial antigens. Circulating immune complexes (CIC) are formed, which help remove antigens from the body.

Immunity to tuberculosis lasts as long as the pathogen is present in the body. Such immunity is called non-sterile or infectious. After the body is freed from mycobacteria, immunity quickly disappears.

Microbiological diagnostics. The material being tested is sputum,

bronchial aspirate, fistula discharge, CSF, urine, feces. Most often, sputum is examined. Basic and additional research methods are used to diagnose tuberculosis.

— bacterioscopic method (light and fluorescence microscopy);

- skin allergy tests;

— molecular biological method (PCR).

A bacterioscopic examination is a repeated direct microscopy of smears from the test material, stained according to Ziehl-Neelsen. Single microorganisms can be detected in preparations if 1 ml of sputum contains at least 10,000-100,000 bacterial cells (method limit). This method is applied:

- when examining persons with symptoms suspicious of tuberculosis (cough with sputum production for more than 3 weeks, pain in chest, hemoptysis, weight loss);

— in persons who have been in contact with tuberculosis patients;

- in persons with x-ray changes in the lungs suspicious for tuberculosis.

If negative results are obtained, they resort to methods of enriching the material: centrifugation (sedimentation) and flotation. The flotation method is most often used.

Centrifugation method - the test material is treated with alkali and centrifuged. A preparation for microscopy is prepared from the sediment.

Flotation method - the material under study is treated with a mixture of alkali and xylene (gasoline, benzene, toluene). The sample is shaken vigorously for 10-15 minutes, distilled water is added and kept for 1-2 hours at room temperature. Droplets of carbohydrate adsorb mycobacteria and float to the surface, forming foam on the surface. A preparation for microscopy is prepared from the resulting foam.

Bacteriological research is carried out by sowing the test material (after treatment with a 6-12% sulfuric acid solution) onto 2-3 nutrient media of different composition simultaneously. As accelerated methods of bacteriological diagnostics, to reduce the time of isolation and identification of the pathogen to 3-4 days, the microculture method (Price method), as well as fully automated commercial broth cultivation systems VASTES MGIT 960 and MV/VasT, are used.

The bacteriological method allows you to obtain a pure culture to determine its virulence and sensitivity to drugs. This method is widely used to monitor the effectiveness of therapy.

A biological sample is the most sensitive, as it can detect from 1 to 5 microbial cells in the material being tested. The method is used when examining biopsy material, as well as when negative results are obtained using the first two research methods. To do this, guinea pigs are injected subcutaneously or intraperitoneally with the test material (1 ml). After 1-2 months, the animals develop generalized tuberculosis with a fatal outcome.

Serological method. RSK, RNGA, enzyme-linked immunosorbent assay, immunoblotting, and determination of CEC have been proposed.

Tuberculin diagnostics is based on determining the body's increased sensitivity to tuberculin (as a result of infection with tuberculosis pathogens or specific vaccination) using skin allergy tests. Tuberculin is used to perform a skin allergy test. Tuberculin is the general name for drugs obtained from human or bovine mycobacteria:

- old Koch tuberculin - ATK (Alt Tuberculin Koch), first obtained in 1880 by R. Koch. It is a filtrate of an autoclaved 5-6-week broth culture of Mycobacterium tuberculosis;

- dry purified tuberculin - PPD (Purified Protein Derivative),

obtained from cultures of M. tuberculosis and M. bovis;

- purified tuberculin prepared by M.A. Linnikova (PPD-L) from cultures of M. tuberculosis and M. bovis.

To diagnose tuberculosis, the Pirquet skin test (scarification test) was initially used. Currently, in order to timely identify

Intradermal Mantoux test is used for primary infection of children and adolescents. When performing the Mantoux test, tuberculin (PPD) is injected strictly intradermally onto the inner surface of the middle third of the forearm until a “button” forms. The test results are taken into account after 48-72 hours based on the presence of a papule. The Mantoux test is evaluated as follows:

- negative - the presence of a reaction from an injection up to 2 mm in diameter;

- doubtful - papule with a diameter of 2-4 mm or hyperemia;

- positive - papule with a diameter of 5-17 mm in children and adolescents and 5-21 mm

- hyperergic - a papule with a diameter of more than 17 mm in children and adolescents and more than 21 mm in adults.

The tuberculin reaction becomes positive 4-6 weeks after infection or vaccination. After vaccination, positive reactions to tuberculin persist for 3-7 years. A positive result should not be considered as a sign of an active process. A positive Mantoux test indicates that a person has previously been infected with mycobacteria. People with positive tuberculin tests are at risk of disease as a result of activation of the primary focus. If in adults a positive reaction indicates infection, then in children who have not previously responded to tuberculin, the appearance of a newly registered positive reaction (tuberculin test turn) indicates a recent infection and serves as an indication for clinical examination and treatment.

If the reaction is negative, there is no risk of activation of the primary focus, but there is a risk of primary infection. A negative test is observed in healthy uninfected individuals, as well as in patients with intermediate forms of tuberculosis.

For rapid diagnosis of tuberculosis, RIF is used using species-specific monoclonal antibodies, laser fluorescence method, microbiochips, as well as PCR, which can reduce research to 2 days.

Treatment. Antibiotic therapy is the main method of treating tuberculosis. According to the degree of effectiveness, anti-tuberculosis drugs are divided into 3 groups:

- group A - the most effective drugs: isoniazid (an antimetabolite, an analogue of isonicotinic acid, inhibits the synthesis of enzymes involved in the synthesis of mycolic acids, which are part of the cell wall of mycobacteria), rifampicin and their derivatives. Drugs have been obtained that have superior medicinal properties to rifampicin (rifapentine and rifabutin), as well as combination drugs (rifater, rifang, etc.);

- group B - drugs of average effectiveness: ethambutol (synthetic drug, inhibits enzymes involved in the synthesis of the cell wall of mycobacteria, is active only against reproducing bacteria), kanamycin, streptomycin, cycloserine, ethionamide (prothionamide), pyrazinamide, florimycin, fluoroquinolone derivatives;

- group C - small anti-tuberculosis drugs (PASK and Tibon or Thiocetozone). This group of drugs is not used in economically developed countries and in Russia.

Strains of mycobacteria resistant to anti-tuberculosis drugs appear very quickly. Therefore, combinations of drugs with different mechanisms of action are used, and drugs are also frequently replaced. This slows down the emergence of resistant forms. In modern treatment regimens, 3-5 drugs are used simultaneously (three- to five-component treatment regimens).

Specific prevention. Specific prevention is carried out by administering a live BCG vaccine (BCG - Bacille Calmette-Guerin). The BCG strain was selected in 1919 by A. Calmette and C. Guerin by long-term passaging of M. bovis on a potato-glycerin medium with the addition of bile.

Vaccination is carried out in newborns on the 3-7th day of life intradermally. An infiltrate with a small nodule in the center forms at the site of vaccine administration. Reverse development of the infiltrate occurs within 3-5 months. Revaccination is carried out at 7 and 14 years of age for persons with a negative Mantoux reaction, therefore, a Mantoux test is performed before it. In newborns with reduced resistance and in regions free from tuberculosis, the less reactogenic BCG-M vaccine is used, containing 2 times less microbes.

After discussing theoretical issues, the teacher explains the procedure for conducting independent work.

1. Students prepare preparations from cultures of non-pathogenic mycobacteria, stain them using Ziehl-Neelsen, microscopy them, and sketch a microscopic picture in a workbook.

2. In their workbook, students sketch a diagram of the laboratory diagnosis of tuberculosis.

7. Assessment of knowledge, skills and abilities on the topic of the lesson:

Answers to questions and activity in class are assessed on a 5-point system.

8. Literature for preparing the topic:

1. Galynkin V., Zaikina N., Kocherovets V. Fundamentals of pharmaceutical microbiology. 2008.

2. Medical microbiology, virology and immunology: a textbook for students medical universities. Ed. A.A. Vorobyov. Textbooks and textbooks benefits for high school. Publisher: Medical Information Agency, 2012. – 702 p.

3. Microbiology: textbook. for students of higher institutions. prof. education, students in the specialty 060301.65 “Pharmacy” / ed. V.V. Zvereva, M.N. Boychenko. – M.: GEOTAR-Media, 2012. – 608 p.: ill.

4. Odegova T.F., Oleshko G.I., Novikova V.V. Microbiology. Textbook for pharmaceutical universities and faculties. - Perm, 2009. - 378 p.

1. Korotyaev A.I. Medical microbiology, immunology and virology: Textbook for medical students. universities / A.I. Korotyaev, S.A. Babichev. — 5th ed., rev. And

add. – St. Petersburg: SpetsLit, 2012. – 759 p.: ill.

2. Medical microbiology: textbook. 4th ed. Pozdeev O.K. / Ed. IN AND. Pokrovsky. – 2010. – 768 p.

3. Guide to medical microbiology. General and sanitary microbiology. Book 1 / Coll. authors // Edited by Labinskaya A.S., Volina E.G. – M.: BINOM Publishing House, 2008. – 1080 pp.: ill.

The guidelines have been revised and supplemented by Professor N.V. Litusov.

Discussed at a meeting of the Department of Microbiology, Virology and Immunology.

In terms of pathogenicity for humans and for individual species Mycobacteria are divided into 2 groups. The first group is the actual pathogenic mycobacterium tuberculosis, of which three types are distinguished. The second group is atypical mycobacteria, among which there are saprophytes - non-pathogenic for humans and animals and opportunistic mycobacteria - under certain conditions they can cause mycobacteriosis, which resembles tuberculosis.

Atypical mycobacteria

According to one classification, they are divided into four groups (depending on growth rate and pigment formation).

• Group I - photochromogenic mycobacteria - form a lemon-yellow pigment during exposure of the culture to light; colonies grow within 2-3 weeks. The source of infection can be cattle, milk and other dairy products.
• Group II - scotochromogenic mycobacteria, which form an orange-yellow pigment in the dark. Distributed in water and soil.
• Group III - non-photochromogenic mycobacteria. Cultures are slightly pigmented or non-pigmented; visible growth appears within 5-10 days. Various in virulence and optimal growth temperature. Occurs in soil, water, and various animals (pigs, sheep).
• Group IV - mycobacteria that grow quickly on nutrient media. Growth is achieved in 2-5 days.

Atypical mycobacteria are detected in 0.3-3% of cultures, most often due to environmental contamination. Their etiological role is considered proven if they are re-sown from pathological material and their growth is characterized by a large number of colonies, and there are no other pathogens of the disease.

The disease caused by atypical strains of Mycobacterium tuberculosis is called mycobacteriosis. The product of their vital activity, sensitin, was obtained from strains of atypical mycobacteria. When sensitin is administered intradermally, a positive reaction occurs in patients with mycobacteriosis. The clinical course of mycobacteriosis resembles tuberculosis, sometimes accompanied by hemoptysis, and rapidly progresses.

Microbiology The causative agent of tuberculosis

M. tuberculosis (Koch's wand) - a thin, straight or slightly curved stick, 1-10 * 0.2-0.6 microns in size, with slightly rounded ends (Fig. 22-1). In young cultures, the rods are longer, and in old ones they tend to branch.

Tuberculosis bacteria capable of forming L-forms that retain the ability to infect, as well as filterable forms, the pathogenetic role of which remains poorly understood. They do not have capsules, but form a microcapsule.

Ziehl-Neelsen method are painted bright red. They contain acid-labile granules (Mukha grains) located in the cytoplasm.

Cultural properties of the causative agent of tuberculosis

Tuberculosis bacilli can grow in both aerobic and facultative anaerobic conditions. Increased CO 2 content (5-10%) promotes faster growth. Optimum temperature 37-38 °C; pH 7.0-7.2. They require the presence of proteins, glycerol, growth factors (biotin, nicotinic acid, riboflavin, etc.), ions (Mg2+ K+, Na+ Fe2+), etc.

For cultivation tuberculosis bacteria The most commonly used are glycerin, potato with bile, egg, semi-synthetic and synthetic media. The most optimal is the Löwenstein-Johnsen environment.

On Wednesdays tubercle bacilli usually form R colonies; under the influence of antibacterial drugs, bacteria can dissociate with the formation of soft and moist S-colonies.

In liquid media tuberculosis bacilli form a dry, wrinkled film (on the 7-10th day), rising to the edges of the test tube; the environment remains transparent. In liquid media, the cord factor is detected - an important differential sign of virulence. The presence of the cord factor causes bacterial cells to come together in microcolonies and their growth in the form of serpentine-shaped braids.

Growth on dense media tuberculosis bacilli noted on the 14th-40th day in the form of a dry, wrinkled coating of yellow, cotton-cream color. Mature colonies resemble cauliflower, are crumbly, poorly wetted with water and have a pleasant odor. Cultures are difficult to remove from the medium and crack when heated. A distinctive feature of M. tuberculosis is the ability to synthesize a significant amount of nicotinic acid (niacin); The niacin test is an important method for differentiating mycobacteria.

Stability of the tuberculosis pathogen in the external environment

The causative agent of tuberculosis is resistant to environmental factors. On the pages of a book, mycobacteria persist for 2-3 months, in street dust - about 2 weeks, in cheese and butter - from 200 to 250 days, in raw milk - 18 days (milk souring does not cause the death of mycobacteria), in a room with diffuse in daylight - 1-5 months, and in damp basements and in garbage pits - up to 6 months.

The optimal growth temperature for the pathogen is 37-38 ° C; at a temperature of 42-43 ° C and below 22 ° C, its growth and reproduction stop. For the avian species of mycobacterium tuberculosis, the optimal growth temperature is 42 ° C. At a temperature of 50 ° C, mycobacteria tuberculosis die after 12 hours, at 70 ° C - after 1 minute. In a protein environment, their stability increases significantly. Thus, mycobacterium tuberculosis in milk can withstand temperatures of 55 ° C for 4 hours, 60 ° C for 1 hour, 70 ° C for 30 minutes, 90 95 ° C for 3 to 5 minutes.

The resistance of Mycobacterium tuberculosis especially increases in dried sputum. To neutralize liquid sputum, they need to be boiled for 5 minutes. In dried sputum, Mycobacterium tuberculosis is killed at 100 ° C after 45 minutes. In a thin layer of liquid sputum, under the influence of ultraviolet rays, Mycobacterium tuberculosis dies in 2-3 minutes, and in dried sputum and in a dark place they can remain viable for 6-12 months. However, when exposed to direct or diffuse solar radiation for 4 hours, dried sputum loses its ability to cause tuberculosis infection in animals. Mycobacterium tuberculosis is not detected in sun-dried sputum.

If sputum enters wastewater or irrigation fields, Mycobacterium tuberculosis retains its virulence for more than 30 days. At a distance of 100 m from the site of wastewater discharge from an anti-tuberculosis sanatorium, Mycobacterium tuberculosis was not detected.

How to avoid contact with mycobacteria

It is immediately worth noting that in our country it is almost impossible not to encounter pathogenic microorganisms that cause tuberculosis.

That is why infants are vaccinated against tuberculosis immediately after birth to reduce the risk of contact with mycobacteria.

Breast milk, timely vaccinations against tuberculosis, an annual Mantoux test for children - this is not always enough to prevent infection. What measures are still needed?

Oddly enough, but anti-tuberculosis or preventive measures can be considered instilling in children a love of sports, a healthy lifestyle, proper nutrition according to age characteristics, hardening, ventilation of premises and wet cleaning in public places, etc.

These are the main factors that contribute to a decrease in immunity and increase the possibility of contracting tuberculosis:

• malnutrition (lack of protein in the diet);
• the presence of chronic diseases such as alcoholism, drug addiction, diabetes, etc.;
• mental trauma;
• old age, etc.

We can say that tuberculosis is not just a complex disease, but also a social phenomenon, which, in fact, is a kind of indicator of how well the population of a particular country lives, how treatment and prevention of the disease is organized.

It is impossible to say for sure whether a person will become infected with tuberculosis or not if he does not have constant contact with the patient.

Much here also depends on the state of the immune system, lifestyle, type of mycobacteria and the presence of the environment in which the microbe will be located.

Many people have been carriers of the infection for years without getting sick themselves. For a weakened body, sometimes one contact with a sick person is enough to become infected.

Therefore, try to avoid contact with infected people, lead an active lifestyle and ventilate the premises more often.

Pathogenesis

Pathogen
tuberculosis enters the body in
composition of fine aerosols.
The pathogen must enter the alveoli,
where they are absorbed by resident
macrophages, the relationship with which
and defines further development
infections. Tuberculosis refers to
classic intramacrophage
infections.

Inside
macrophages tuberculosis bacteria
are resistant to bactericidal
phagocyte factors due to powerful
lipid membrane. As a result
interactions between mycobacteria and macrophages
under the influence of virulence factors
granulomatous inflammation develops
type.

Granuloma
develops immediately after infection,
but later she gets a powerful
impulse for development when in the body
T-lymphocytes appear, sensitized
to the pathogen.

Pre-immune
granuloma after 2–3 weeks under the influence
T lymphocytes are converted into specific
(postimmune), which is called
tuberculoma.

From
lungs the tuberculosis bacillus enters
to regional lymph nodes, then
- into the bloodstream. Further events are connected
with specific inflammation, based
which is the cause of the allergic reaction
for bacterial antigens.

Path
airborne infection. Source
- a sick person who is in acute
period excretes tuberculosis with sputum
sticks.

Most
pulmonary tuberculosis is common,
but both the intestines and
musculoskeletal system, and genitourinary
system, etc.

Highlight
two pathogenetic variants of tuberculosis.

1. Primary
tuberculosis. Occurs in individuals who have not previously
who had contact with the pathogen.
Infection occurs in childhood
age or adolescence.
Develops without allergy to the pathogen.
In the penetration zone, the pathogen is captured
macrophages, nonspecific develops
granulomatous reaction. Bacteria are easy
pass this barrier, quickly penetrate
to regional lymph nodes, blood
and various organs.

Through
2–3 weeks the primary one is formed
tuberculosis complex, which includes
myself:

1) primary
affect - a focus in the lung tissue;

2) lymphadenitis
– inflammation of regional lymph nodes;

3) lymphangitis
– inflammation of the lymphatic vessels.

Most
often it heals itself, undergoes
fibrosis and calcification (Ghon's lesion). IN
bacteria persist in this focus, but
are not released into the external environment.

IN
in other cases, acute
tuberculosis.

2. Secondary
tuberculosis. It occurs chronically.
Occurs when the primary
outbreak (after 5 years or more). Maybe
also reinfection from the outside.

Development
secondary tuberculosis contribute
unfavorable living conditions, chronic
diseases, alcoholism, stress, etc.

Peculiarities
immunity in tuberculosis:

1) non-sterile,
supported by those bacteria that
persist in the body;

2) unstable,
i.e. it does not protect against reactivation
endogenous infection and reinfection from the outside;

3) antibodies
are formed, but they do not have a protective
values;

4) main
mechanism of immunity – cellular;
infectious is of primary importance
allergy.

Morphology and cultural properties

Pathogen
belongs to the genus Mycobakterium, species M. tuberculesis.

This
thin sticks, slightly curved, spore
and do not form capsules. Cell wall
surrounded by a layer of glycopeptides, which
called mycosides (microcapsules).

Tuberculosis
the wand is difficult to perceive ordinary
dyes (colored according to Gram
24–30 hours). Gram positive.

Tuberculosis
the rod has structural features and
chemical composition of the cell wall,
which affect all biological
properties. main feature- V
the cell wall contains a large
amount of lipids (up to 60%). Majority
of which are mycolic acids, which
enter the cell wall framework, where
are in the form of free glycopeptides,
included in the cord factors.
Cord factors determine character
growth in the form of cords.

IN
cell wall composition includes
lipoarabinomanan. Its terminal
fragments – cap – determine the ability
pathogen specifically bind
with macrophage receptors.

Mycobacteria
tuberculosis are stained by Ziehl-Neelsen.
This method is based on acid resistance
mycobacteria, which is determined
features of the chemical composition
cell wall.

IN
as a result of treatment with anti-tuberculosis
drugs can kill the pathogen
acid resistance.

For
Mycobacterium tuberculosis is characteristic
pronounced polymorphism. In their
the cytoplasmic membrane are found
characteristic inclusions are Mukha grains.
Mycobacteria in the human body can
go into L-forms.

By
Aerobic type of energy production. By
temperature requirements – mesophiles.

Reproduction
they happen very slowly, time
generation – 14–16 hours. This is due to
pronounced hydrophobicity, which
due to high lipid content.
This makes it difficult to supply nutrients
substances into the cell, which reduces metabolic
cell activity. Apparent growth by
Wednesdays – 21–28 days.

Mycobacteria
demanding on nutrient media.
Growth factors – glycerol, amino acids.
They grow on potato-glycerin,
egg-glycerin and synthetic
environments In all these environments it is necessary
add substances that inhibit
growth of contaminating flora.

On
dense nutrient media are formed
characteristic colonies: wrinkled, dry,
with uneven edges, do not merge with each other
with a friend.

IN
in liquid media they grow in the form of a film.
The film is initially tender, dry, and over time
thickens, becomes lumpy and wrinkled
with a yellowish tint. Wednesday
opaque.

Tuberculosis
bacteria have a certain
biochemical activity, and study
it is used for differentiation
tuberculosis pathogen from others
representatives of the group.

Factors
pathogenicity:

Mykolovy
acids;

cord factor;

sulfatides;

mycosides;

lipoarabinomanan.

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Bacteria that cause tuberculosis

Let's say a few words about the disease itself. Tuberculosis is a disease that is classified as infectious.

The disease affects not only humans, but also animals. This disease is always clinically realized, has a genetic predisposition and depends on environmental factors.

As a rule, tuberculosis affects the lungs, but other organs and systems can also be affected (lymph nodes, intestines, bones, kidneys, reproductive organs, central nervous system, etc.).

As the disease develops, characteristic granulomas appear; these are small grains that look like tubercles and nodules.

In ancient times, tuberculosis was called “consumption.” And only in 1882 Heinrich Koch (German microbiologist) was able to discover the causative agent of the disease and remove it in a serum medium.

For his research in 1905, the scientist received the Nobel Prize. What other microorganisms cause tuberculosis?

Microbiology has found the answer to this question. The causative agents of tuberculosis are specific mycobacteria that belong to the group Mycobacterium tuberculosis complex (M. tuberculosis and other closely related species.

In total, the scientific world knows more than 150 species of such bacteria. This microorganism is traditionally called “Koch’s bacillus” in honor of the famous German scientist who discovered this bacterium to the scientific world.

In humans, tuberculosis can be caused by one of three types of mycobacteria:

1. "Koch's stick", in Latin called M. Tuberculоsis. This microorganism causes about 92% of all cases of the disease.
2. Bovine species, M. bovis. This tuberculosis pathogen occurs in 5% of cases.
3. An intermediate type, M. africanum, which most often affects residents of South Africa and occurs in 3% of cases.

It is very rare that you can become infected with tuberculosis from mycobacteria of the avian or mouse type, which are very rare and more common in people infected with immunodeficiency.

Genetics and variability of mycobacteria

The carriers of genetic information of Mycobacterium tuberculosis are chromosomes and extrachromosomal elements - plasmids. The main difference between chromosomes and plasmids is their size. A plasmid is much smaller than a chromosome and therefore carries less genetic information. It is due to its small size that the plasmid is well adapted to transfer genetic information from one mycobacterial cell to another.

Plasmids can interact with the chromosome. The resistance genes of Mycobacterium tuberculosis against chemotherapy are localized both in chromosomes and in plasmids.

Mycobacteria have DNA that functions as the main carrier of genetic information. The sequence of nucleotides in a DNA molecule is a gene. The genetic information carried by DNA is not something stable and unchanging. It is changeable and evolving, improving. Single mutations are usually not accompanied by large changes in the information contained in the genome. A single strain can produce several different phenotypes (or traits that result from the action of genes under certain conditions) that are resistant to a particular antimycobacterial drug.

The mutation can also manifest itself in changes in the morphology of the colonies. Thus, if the virulence of Mycobacterium tuberculosis is changed, the morphology of the mutant colonies may also change.

Transduction is the transfer of genetic material (DNA particles) from one mycobacterium (donor) to another (recipient), which leads to a change in the genotype of the recipient mycobacterium.

Transformation is the inclusion of a DNA fragment of another mycobacterium (donor) into the chromosome or plasmid of a mycobacterium (recipient) as a result of the transfer of isolated DNA.

Conjugation- this is a contact between Mycobacterium tuberculosis cells, during which the transfer of genetic material (DNA) from one cell to another occurs.

Transfection is the reproduction of the viral form of Mycobacterium tuberculosis in a cell that is infected with isolated viral nucleic acid.

The hypothetical pathways outlined for the transfer of genetic information have not yet been studied. However, there is no doubt that these genetic processes are the basis for the emergence of drug resistance both in individual mycobacteria and in the entire bacterial population present in the patient’s body.

Antigens

Mycobacteria have specific species and interspecific and even intergeneric antigenic relationships. Different antigens have been identified in individual strains. However, all mycobacteria, without exception, contain substances that are resistant to heat and proteolytic enzymes - polysaccharides, which are a common antigen.

In addition, different types of mycobacteria have their own specific antigens. A. P. Lysenko (1987) proved that all strains of M. bovis have an identical antigenic spectrum with 8 antigens, of which 5-6 were generic and reacted with antisera to mycobacteria of other species: 6 - with M. tuberculosis, 3-5 - M. kansasii, etc.

Diagnosis of MBT

To diagnose tuberculosis, tuberculodiagnostics is used, which consists of the body’s reaction to the introduction of tuberculin. Tuberculin is obtained from bacilli (previously killed and dried), it contains molecules characteristic of MBT.

If the body contains similar bacteria with similar chemical composition, then an allergic reaction occurs (a papule forms at the site of intradermal administration of the drug).

Laboratory methods used:

• interferon test;
• ELISA (detects antibodies to the rod, indicates the fact of infection);
• quantiferon test.

A blood test for tuberculosis reveals an increase in the number of leukocytes and an accelerated ESR. In biochemical analysis, the level of globulin coefficient decreases in tuberculosis.

When examining sputum from carriers of Koch bacteria, an admixture of blood and pus, as well as protein content (with tuberculosis, its amount increases), etc. can be detected.

Lymph analysis can detect disseminated tuberculosis. In extrapulmonary forms of the disease, urine and various tissues are examined.

The most accessible hardware diagnostic method is fluorography. Allows you to detect pathological changes in lung tissue and determine their location.

Computed tomography is performed to identify the location of the Koch bacterium and confirm the diagnosis.

The bacilli quickly become resistant to drugs and pass on genetic memory to their offspring.

Drug resistance of Mycobacterium tuberculosis occurs after mutations in the MTB genes (usually as a result of the use of incorrect chemotherapy regimens).

Treatment and prevention

• ventilation of the room;
• strengthening immunity;
• early diagnosis and treatment;
• rejection of bad habits.

Treatment and prevention

In patients who become ill for the first time, bacteria are more easily affected by drugs. It is more difficult to treat relapses, since the Koch bacillus has the ability to quickly adapt.

When prescribing treatment, the types of development of specific processes are taken into account. Etiotropic therapy consists of 2 stages: intensive and prolonged, carried out according to schemes. The 3-component regimen includes the use of Isoniazid, PAS, and Streptomycin. The 4-component regimen includes Kanamycin, Rifampicin, Ethionamide, Phtivazide. When treating complex multi-resistant forms of pathology, a 5-component regimen is used: Ciprofloxacin is added to the previous option.

The patient is prescribed a complex diet with the obligatory introduction of proteins, carbohydrates, and fats into the diet.

Sanatorium-resort treatment helps saturate the lungs with oxygen, stopping the development and growth of Koch bacteria.

Surgical treatment is used to neutralize a lesion that poses a threat to life. Part of the lung or the entire organ is removed.

Infection with Mycobacterium tuberculosis does not always lead to the development of the disease. Immunity to tuberculosis can develop after specific prophylaxis (immunization with the BCG vaccine).

Nonspecific prevention includes:

• ventilation of the room;
• strengthening immunity;
• early diagnosis and treatment;
• fluorography for adults and Mantoux test for children;
• rejection of bad habits.

Using preventive measures, you can prevent the development of the disease.

Types of mycobacteriosis

There are three types of mycobacteriosis, which depend on the type of mycobacteria and the immune status of the body:

1. Generalized infection with the development of pathological changes visible to the naked eye externally resemble tuberculosis, but histologically they are somewhat different from them. Diffuse interstitial changes without granulomas and decay cavities are found in the lungs. The main signs are fever, bilateral dissemination in the middle and lower parts of the lungs, anemia, neutropenia, chronic diarrhea and abdominal pain. The diagnosis is confirmed by the presence of the pathogen in sputum, stool or biopsy. The effectiveness of treatment is low, the mortality rate is high and reaches 20%. Effective for the treatment of mycobacteriosis are cycloserine, ethambutol, kanamycin, rifampicin and partially streptomycin.

2. Localized infection - characterized by the presence of macro- and microscopic lesions detected in certain areas of the body.

3. An infection that occurs without the development of visible lesions; The pathogen is located in the lymph nodes.

Tuberculosis in humans predominantly (95-97%) occurs as a result of infection with human, less often (3-5%) bovine and, incidentally, avian species of Mycobacterium tuberculosis. M. africanum causes tuberculosis in humans in tropical Africa.

M. tuberculosis

Mycobacterium tuberculosis has the form of thin, long or short, straight or curved rods, 1.0-4.0 µm long and 0.3-0.6 µm in diameter; nonmotile, do not form spores or capsules, gram-positive, have high polymorphism.

Mycobacterium tuberculosis of the human species is thinner and longer than that of the bovine species. Mycobacteria of the bovine species are less pathogenic for humans, and the disease caused by them is much less common. To determine the MBT of the human species, the niacin test is used. It is based on the fact that MBT of this species secrete more niacin (nicotinic acid).

Young bacteria are homogeneous; during their aging, granularity (Much grains) is formed, which is studied in more detail by electron microscopy. The granular form of Mycobacterium tuberculosis is also formed under the influence of antimycobacterial drugs. After introducing grains to animals, they develop cachexia, enlarged lymph nodes or tuberculosis with the development of typical strains of Mycobacterium tuberculosis. Described splintered forms of Mycobacterium tuberculosis. The causative agent of tuberculosis can also exist in the form of filterable forms.

Under the influence of anti-tuberculosis drugs, the morphological and physico-chemical properties of Mycobacterium tuberculosis change. Mycobacteria become short, approaching cocobacillus, their acid resistance decreases, therefore, when stained according to Ziehl-Neelsen, they become discolored and are not detected.

Composition of mycobacteria

Mycobacteria consists of a cell membrane and cytoplasm. The cell membrane is three-layered and consists of outer, middle and inner layers. In virulent mycobacteria it has a thickness of 230-250 nm.

The outer layer surrounding the cell is called the microcapsule. It is formed by polysaccharides and contains fibrils. The microcapsule can surround an entire population of mycobacteria, and can also be placed where mycobacteria adhere to each other. The absence or presence of growth, its intensity and the composition of the microcapsule depend on how much cord factor is extracted from the cytoplasm into the cell wall. The more cord factor is extracted, the better the microcapsule is expressed in Mycobacterium tuberculosis.

The cell membrane is involved in the regulation of metabolic processes. It contains species-specific antigens, due to which the cell wall is the locus where delayed allergic hypersensitivity reactions and the formation of antibodies occur, since it, as the actual surface structure of the bacterial cell, is the first to contact the tissues of the macroorganism.

Under the cell membrane there is a three-layer cytoplasmic membrane, closely adjacent to the cytoplasm. It consists of lipoprotein complexes. Processes occur in it that determine the specificity of the reaction of mycobacteria to environmental factors.

The cytoplasmic membrane of Mycobacterium tuberculosis, through its centripetal invagination, forms an intracytoplasmic membrane system in the cytoplasm - mesos. Mesosomes are semi-functional structures. They contain many enzyme systems. They participate in the synthesis and formation of the cell wall and act as an intermediary between the nucleus and cytoplasm of the bacterial cell.

The cytoplasm of mycobacteria consists of granules and inclusions. In young Mycobacterium tuberculosis, the cytoplasm is more homogeneous and compact than in old ones, which have more vacuoles and cavities in the cytoplasm. The bulk of granular inclusions are made up of ribosomes, located in the cytoplasm in a free state or forming polysomes - an accumulation of ribosomes. Ribosomes consist of RNA and protein and synthesize specific proteins.

The immunogenicity of Mycobacterium tuberculosis is mainly due to antigenic complexes contained in the membranes of mycobacterial cells. Ribosomes, ribosomal protein and cytoplasm of mycobacteria have antigenic activity in delayed reactions.

Pathogenicity of Mycobacterium tuberculosis

Pathogenicity is a species property of Mycobacterium tuberculosis, which turns out to be able to cause disease. The main pathogenicity factor is toxic glycolipids - cord factor. This is a substance that glues virulent mycobacteria together, so that they grow on nutrient media in the form of ropes. Cord factor causes a toxic effect on tissue and protects tuberculosis bacilli from phagocytosis by blocking oxidative phosphorylation in macrophage mitochondria. Therefore, when absorbed by phagocytes, they multiply in them and cause their death. Acid-resistant saprophytes do not form a cord factor.

Virulence- degree of pathogenicity; the possibility of growth and reproduction of mycobacteria in a certain macroorganism and the ability to cause specific pathological changes in organs. A strain of mycobacteria is considered virulent when it causes tuberculosis in a dose of 0.1-0.01 mg, and after 2 months - the death of a Guinea pig weighing 250-300 g. When, after administration of this dose, the animal dies after 5-6 months, then this strain is considered weakly virulent. Virulence is not an immutable property of mycobacteria. It decreases with aging of the culture or cultivation on artificial nutrient media and during the treatment of patients. During passages on animals or in cases of exacerbation of the tuberculosis process, virulence increases.

Reproduction of Mycobacterium tuberculosis

Mycobacterium tuberculosis reproduces by transverse division, branching or budding of individual grains. Mycobacterium tuberculosis grows on nutrient media in the presence of oxygen. But they are facultative aerobes, i.e. They grow and when there is no access to air, they get oxygen from carbohydrates. Therefore, growing mycobacteria requires a nutrient medium rich in carbohydrates.

Dense media containing eggs, milk, potatoes, and glycerin are effective. The most commonly used environments are Levenshtein-Jensen, Gelberg, Finn-2, Middlebrook, and Ogawa. Mycobacterium tuberculosis grows slowly. The first colonies appear on the 12-30th day, and sometimes after 2 months. To ensure the growth of Mycobacterium tuberculosis, 3-6% glycerol is added to the nutrient media. Mycobacteria grow better in a slightly alkaline environment, although they can also grow in a neutral environment.

Adding bile to the nutrient medium slows down their growth. This circumstance was used by Calmette and Guerin when developing a vaccine. On liquid nutrient media with the addition of glycerol, Mycobacterium tuberculosis grows in the form of a film. Colonies of mycobacteria can be rough (K.-variants) and less often - smooth, merging with each other (8-variants). K.-variants of mycobacteria are virulent for humans and animals, and 8-variants are often non-virulent.

Biochemical features

Let's talk about the bacterial component and the habitat of microorganisms. Mycobacterium tuberculosis is very sensitive to direct sunlight.

So, in hot weather, in the sputum in which infections live, they can die within two hours.

They are especially sensitive to ultraviolet light. Mycobacteria also die when heated.

At 60 degrees and a humid environment they will die within an hour, at 65 degrees - within 15 minutes, at 80 degrees - within 5 minutes.

Interestingly, such bacteria can live in fresh, unboiled milk for 10 days, and in butter or hard cheeses for several months. Such microorganisms are more resistant to most disinfectants.

Thus, a five percent solution of phenol with 10% Lysol can destroy bacilli within 24 hours! And formalin solution - after 12 hours.

The stick is freeze resistant. It can live in wastewater for about a year, in manure - up to 10 years. Even in a completely dried state, it can be viable for 3 years!

Without going into the most complex biochemical processes occurring during the metabolism of mycobacteria, we can briefly note the following: the cells of tuberculosis bacteria are very flexible, changeable and resistant to various changes in the environment.

Under certain conditions, they can live for several years, “waiting” for prey! That is why sometimes it is not enough just to be vaccinated against this disease on time.

What anti-tuberculosis prophylactic agents should be used then?

Forms of behavior

Once in the human body, the bacterium begins to multiply (if the body’s defenses are weakened) or become inactive (if the immune system is good).

Physiology of Mycobacterium tuberculosis: depending on the activity of oxidative enzymes, it is possible to distinguish between saprophytic and pathogenic species, the mechanism of drug resistance, and the virulence of microorganisms.

A decrease in population resistance to tuberculosis and frequent and prolonged use of antibiotics have caused the variability of the pathogen.

Potentially dangerous to humans are: M.konsasii, M.scrofulaceum, M.marinum, M.xeponi, M.fortuitum, M.ulcerans, M.chelonei, which cause tuberculosis in humans.

To identify the causative agent of tuberculosis, the PCR method is used, in which the DNA of Mycobacterium tuberculosis is detected in a sample of biomaterial.

Infectious granuloma is the main morphological component of the inflammatory process caused by the penetration of mycobacteria into organs.

As a result of inflammation, specific granulomas form and damage the body (usually mature, but sometimes pathology develops at a young age).

In the absence of resistance from the body, MBT develops and provokes an active form of the disease. The more common form is the closed form, which is difficult to detect: the carrier rarely experiences deterioration in health.

The classification of Mycobacterium tuberculosis includes biological and morphological characteristics. Mycobacteria are distinguished:

• on the effect on the body;
• by the ability to use nutrients;
• by growth at different temperatures.

Diagnosis of MBT

Nowadays, there are the following methods for detecting Mycobacterium tuberculosis:

• clinical blood test - if Koch’s bacillus progresses, then this test will show an increased level of leukocytes;
• biochemical blood test - it helps to detect albumin - globulin coefficient, the level of which in acute tuberculosis is below normal. Biochemical analysis will also show the content of angiotensin, a converting enzyme in the blood, the activity of which increases with fibrotic changes in the lungs;
• sputum examination - the sputum of a carrier of Koch's bacillus may contain pus and blood impurities (an open form of the disease). This analysis will determine the amount of protein in the sputum (a large amount of protein indicates a disease), determine the M. tuberculosis bacilli and other substances (cholesterol, calcium salts, elastic fibers). These cumulative findings indicate lung collapse;
• microbiological diagnostics - to detect MBT, sputum is taken from the patient and placed in a sterile container. Then laboratory workers observe the growth pattern of bacteria, their resistance (resistance) to antibiotics and other drugs. Microbiological analysis can be performed within 20-90 days;
• X-ray - thanks to this main method for determining MBT, you can clearly see the presence of mycobacteria in the human lungs, the difference between pneumonia and tuberculosis, and determine the stage of spread of the virus in the lungs;
• Mantoux test is a type of tuberculin test made by injecting tuberculin under the skin. If the diameter of the papule 2-3 days after administration of the substance is more than 10 mm, then the patient is at risk or infected with tuberculosis;
• Pirquet skin test - this test is carried out by applying a scratch to the patient’s skin in the forearm area with a scarifier treated with tuberculin. The graduated Pirquet test is used to detect M. tuberculosis in children and adolescents. According to the results of the analysis, if after 2-3 days the patient has a papule with a width of 4 mm or more, then there is a possibility of infection with Koch’s bacillus.

If it was not possible to detect MBT using the above methods, then it is necessary to conduct additional research in the following ways:

• computed tomography – thanks to this research method, it is possible to identify the location of the microbe Mycobactérium tuberculosis, an image of the damaged organ and establish the disease;
• serological, immunological tests of blood and sputum:

1. ELISA – enzyme immunoassay of blood. Using this test, you can detect antibodies to Mycobacterium tuberculosis, which indicate that the patient is infected with MTB;
2. RPGA - helps to determine the active extrapulmonary form of the disease, establish the type of harmful mycobacteria, and also confirm the correctness of the diagnosis;
3. Quantiferon test - the high accuracy of this blood test (up to 99%) will clearly indicate the presence of MBT. The test result can be found out in a few hours.

• biopsy - this analysis is performed by taking a puncture from an infected organ (lung, pleura, lymph nodes) for further examination. The analysis result is accurate in 80-90% of cases;
• bronchoscopy – this appointment is performed if there are symptoms of bronchial tuberculosis. This method reveals changes in the mucous membrane of large bronchi, their narrowing and the presence of holes in the bronchi.

In addition to the above, there are other ways to study Koch's bacillus, for example, urine analysis (for tuberculosis of the urinary tract and kidneys, bones), fluorescent microscopy, which detects MBT in small quantities, etc.

Variability of mycobacteria

Variabilitymycobacteria- this is their ability to acquire new and/or lose old characteristics. Due to the fact that Mycobacterium tuberculosis has a short generation period, a high frequency of mutations and recombinations, and the exchange of genetic information, the variability in them is very high and frequent (N. A. Vasiliev et al., 1990).

There are phenotypic and genotypic variability. A phenotypic mutation is also called a modification mutation, which is characterized by a high frequency of changes and their frequent reversion to the original form, adaptation to changes in the external environment, and no changes in the genetic code. It is not hereditary.

Genotypic mutation occurs due to mutations and recombinations.

Mutations- these are stable inherited changes in the nucleotide composition of the mycobacterial genome, including plasmids. They can be spontaneous or induced. Spontaneous mutations occur at a gene-specific rate. Most of them are the result of errors in DNA replication and repair. Induced mutations are possible as a result of exposure to mutagens (ultraviolet; ionizing radiation, chemicals, etc.). Mutations often lead to the appearance of a new trait in the phenotype or the loss of an old trait (compared to the parental form).

Recombinationsgenetic- this is the process of formation of offspring containing donor characteristics; and the recipient.

One of the types of variability of Mycobacterium tuberculosis is the formation of filterableforms. These are very small forms, invisible under ordinary microscopy, having very weak virulence; they can only be detected during reversion, using repeated passages on guinea pigs. In these cases, acid-fast bacilli with very low virulence are sometimes found.

Filterable forms are small fragments of Mycobacterium tuberculosis, formed under unfavorable living conditions and capable of reversion. The nature of these forms, their structure, as well as their significance in the pathogenesis of tuberculosis have not yet been fully established.

Types of drug resistance

Primary drug resistance is resistance found in newly diagnosed patients who have never taken anti-tuberculosis drugs.

Initial drug resistance is MBT resistance detected in newly diagnosed patients treated with anti-tuberculosis drugs for no more than 4 weeks or in patients in the absence of data on previous treatment. Secondary (acquired) drug resistance - MBT resistance, was found in patients who were prescribed anti-tuberculosis drugs for more than 4 weeks. Monoresistance is the resistance of MBT against 1 of 5 first-line drugs (isoniazid, streptomycin, rifampicin, ethambutol, pyrazinamide).

In Ukraine, the incidence of primary resistance of the tuberculosis pathogen against first-line drugs is observed in 23-25%, and secondary resistance in 55-56% of cases. Multidrug resistance is the resistance of MBT against two or more drugs. Multidrug resistance is a type of multiple drug resistance, and namely, the resistance of the pathogen only against the combination of isoniazid + rifampicin or several other drugs.

The result of determining the sensitivity of Mycobacterium tuberculosis to anti-tuberculosis drugs is called an antibiogram.

Causesdrug resistance:

1. Biological - insufficient concentration of the drug, individual characteristics of the patient’s body (rate of drug inactivation)

2. Reasons caused by the patient - contact with patients with chemoresistant tuberculosis, irregular intake of drugs, premature cessation of medication, unsatisfactory tolerability of drugs, inadequate treatment.

3. Factors caused by the disease - when changing the doses of drugs, with a large amount of MBT in the areas of the affected organ, a certain pH may arise, which interferes with the active effect of the drugs, treatment with one drug, insufficient dose or duration of treatment.

Genome of Mycobacterium tuberculosis

IN last years Genetic studies of the M. tuberculosis strain were intensively carried out. The amount of guanine cytosine bases that are distributed on the deoxyribonucleic acid (DNA) helix is ​​65.5%. The genome contains many insertion sequences, multigene families, amplified (duplicated) sites of its own metabolism.

RNA molecules encode about 50 genes, in particular:

• three types of ribosomal RNAs, which are synthesized from a unique ribosomal operon;
• genes encoding 108-RNA are included in the process of protein destruction (it has been revealed that these 108-RNAs are encoded by so-called abnormal and RNA messengers);
• genes encoding the RNA component RNase P;
• transfer RNA genes.

M. tuberculosis has 11 receptor-dependent histidine kinases, several cytoplasmic kinases, and few genes involved in regulatory cascades. M. tuberculosis is a group of eukaryotic serine thyreonine protein kinases responsible for phosphorylation in the bacterial cell.

To carry out lipid metabolism, approximately 250 enzymes are synthesized in M. tuberculosis. The oxidation of fatty acids is ensured by the following enzyme systems:

1. RabA / RabB-R-oxidase complexes.

2. Thirty-six acyl-CoA synthetases and a group of thirty-six acyl-CoA synthetases-linked proteins.

3. Five enzymes complete the oxidation cycle (thiolysis reaction of 3 ketoesters).

4. Four hydroxyacyl-CoA dehydrogenases.

5. Twenty-one types of proteins of the enoyl-CoA-hydratase isomerase group.

6. Acetyl-CoA-C-acetyltransferases.

PathogenicityM. tuberculosis is also caused by such factors as: 1) antioxidase catalase-peroxidase system;

2) sigma factor;

3) MSE operon, encoding intracellular invasion proteins;

4) phospholipase C;

5) enzymes producing cell wall components;

6) hematoglobin-like P-binding proteins, which ensure long-term anaerobic existence of mycobacteria;

7) esterases and lipases;

8) significant antigenic lability;

9) the presence of various ways to ensure antibiotic resistance;

10) the presence of acteriocins with a cytotoxic effect (some polyketins).

Chemical composition of Mycobacterium tuberculosis

The chemical composition of Mycobacterium tuberculosis has been studied quite well. They contain 80% water and 2-3% ash. Half of the dry residue consists of proteins, mainly tuberculoproteins, lipids - from 8 to 40%, and the same amount of polysaccharides. It is assumed that tuberculoproteins are full-fledged antigens and can cause a state of anaphylaxis in animals. The lipid fraction leads to resistance of the tuberculosis pathogen, and the polysaccharide fraction is involved in immunogenesis.

Tuberculoproteins and lipid fractions determine the toxicity of Mycobacterium tuberculosis, which is inherent not only in living but also in killed microorganisms. Three lipid fractions have been identified: phosphatidic, fatty and waxy. The high lipid content distinguishes Mycobacterium tuberculosis from other types of microorganisms and leads to the following properties:

1. Resistance to acids, alkalis and alcohols (mainly due to the presence of mycolic acid).

2. Resistant against common disinfectants.

3. Pathogenicity of tuberculous mycobacteria.

Exotoxins have not been identified, but the mycobacterial cells themselves are toxic - they lead to partial or complete breakdown of leukocytes. In the inorganic residue of mycobacterium tuberculosis, iron, magnesium, manganese, potassium, sodium, and cobalt salts are determined. The antigenic structure of mycobacteria is complex and not yet fully understood.