Mycobacterium tuberculosis: features of these microorganisms

Mycobacterium tuberculosis (Koch sticks) are 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 decay, sunlight or to drying. These microorganisms are poorly colored with aniline dyes and reveal high pathogenicity and hydrophobicity.

It should be noted that the special morphological 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 these bacteria, 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 reproduced form a dry wrinkled coating of cream color, the appearance of their colonies resemble cauliflower.

Pathogenetic features

The main factor of pathogenicity is the "cord factor". These are glycolipids, which protect Koch's rods from phagocytosis and predetermine toxic damage to the tissues of a sick person. It is also worth noting 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 through the respiratory tract, where they are captured by macrophages. Later, bronchopneumonic focus forms at the site of these bacteria, and regional lymph nodes also 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 remain in the body for a long time and can become active after many years.

I must say that early detection of tuberculosis increases the chances of a favorable outcome of the disease. To date, more and more often use the latest diagnostic methods, among which the leading role is played by the polymerase chain reaction.

When conducting PCR on tuberculosis, it is possible to detect the DNA of the Koch sticks, even in cases of their minimal amount, when it is not possible 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 drugs. 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.