Mycobacterium tuberculosis: features of these microorganisms
Mycobacterium tuberculosis (Koch sticks) -Gram-positive rod-shaped bacteria that can form threadlike structures. They are acid-fast and immobile, contain a lot of lipids and wax in their walls, which predetermines their resistance to decontamination, sunlight or to drying. These microorganisms are poorly colored with aniline dyes and reveal high pathogenicity and hydrophobicity.
It should be noted that special morphologicalthe types of these bacteria are coccoid structures and l-forms, although most of them are thin and straight, slightly curved sticks. In addition, Mycobacterium tuberculosis contains in the cytoplasm Fly grain (specific acid-labile granules).
If we talk about the cultural properties of databacteria, they are facultative anaerobes or aerobes. Their characteristic feature is very slow growth and the need for protein and glycerin for successful reproduction. On liquid media, these microorganisms form a surface film. On dense nutrient media, mycobacterium tuberculosis, when multiplied, forms a dry wrinkled coating of cream color, resembling cauliflower in appearance of their colony.
The main factor of pathogenicity is the "cord factor". These are glycolipids, which protect Koch sticks from phagocytosis and predetermine toxic damage to the tissues of a sick person. It should also be noted that mycobacterium tuberculosis is characterized by a complex set of antigens, so their identification by antigenic properties is practically not used.
Is TB transmitted? In the epidemiology of this disease, three routes of infection are identified. It is airborne, through infected milk of animals (alimentary) and air-dust. I must say that a person during his life often contacts with the causative agents of tuberculosis, but the disease does not develop, which depends on the resistance of the organism.
Koch's rods most often penetrate throughrespiratory tract, where they are captured by macrophages. In the future, bronchopneumonic focus forms at the site of these bacteria, and regional lymph nodes develop. The primary focus of infection can provoke pneumonia and generalization of the tuberculosis process. With high resistance of the organism, mycobacteria cease to multiply. At the same time, they persist for a long time in the body and can become active after many years.
It should be noted that early detection of tuberculosisincreases the chances of a favorable outcome of the disease. To date, increasingly using the latest diagnostic methods, among which the leading place is the polymerase chain reaction.
When conducting PCR on tuberculosis can detectThe DNA of the Koch sticks, even in cases of their minimal amount, when it is impossible to confirm the development of the disease by any other methods. In addition, using PCR, it is easy to detect the resistance of mycobacteria to individual medicinal products. To do this, it is sufficient to copy the genes that are responsible for the resistance of bacteria to rifampicin, isoniazid or other medicinal substance, which takes no more than 48 hours.