Mycobacterium tuberculosis (Koch's rods) are Gram-positive, rod-shaped bacteria that can form filamentous structures. They are acid-resistant and immobile, contain a lot of lipids and wax in their wall, which predetermines their resistance to substances, sunlight or drying. These microorganisms are poorly stained with aniline dyes and exhibit high pathogenicity and hydrophobicity.
It should be noted that the special morphological types of these bacteria are coccoid structures and L-shapes, although most of them are thin and straight, slightly curved rods. In addition, Mycobacterium tuberculosis contains Fly grains (specific acid-labile granules) in the cytoplasm.
If we talk about the cultural properties of these bacteria, then 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 during reproduction form a dry wrinkledcream-colored coating, in appearance their colonies resemble cauliflower.
Pathogenetic features
The main factor of pathogenicity is the "cord factor". These are glycolipids that protect Koch's sticks from phagocytosis and predetermine the 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 tuberculosis transmitted? In the epidemiology of this disease, three ways of transmission of infection are distinguished. It is airborne, through contaminated animal milk (alimentary) and airborne. I must say that a person in the course of life quite often comes into contact with tuberculosis pathogens, but the disease does not develop, which depends on the body's resistance.
Koch's sticks most often penetrate through the respiratory tract, where they are captured by macrophages. Later, a bronchopneumonic focus is formed at the site of entry of these bacteria, and inflammation of the regional lymph nodes also develops. The primary focus of infection can provoke pneumonia and generalization of the tuberculosis process. With high resistance of the body, mycobacteria stop multiplying. At the same time, they remain in the body for a long time and can be activated after many years.
I must say that early detection of tuberculosis increases the chances of a favorable outcome of the disease. Today, more and more oftenthe latest diagnostic methods, among which the leading place is occupied by the polymerase chain reaction.
When conducting PCR for tuberculosis, it is possible to detect Koch's bacillus DNA even in cases of their minimal amount, when it is not possible to confirm the development of the disease by any other means. In addition, using PCR, it is easy to detect the resistance of mycobacteria to individual drugs. To do this, it is enough to copy the genes that are responsible for the resistance of bacteria to rifampicin, isoniazid or another drug, which takes no more than 48 hours.
