2.2 Ways and means of transmission of tuberculosis infection


The basic source of MBT is the tuberculosis patient, spreading MBT (bacillary expectorator).

The pesthole of the tubercular infection becomes dangerous when the patients suffer by the opened form of tuberculosis it means that he is MBT expectorator. The special importance at tuberculosis infection has direct, long and close contact of the healthy person with MBT expectorator. It can occur more often in family, apartment or community, in which the tuberculosis patient expectorates MBT for a long time. The danger of dissemination of the infectious agent is eliminated if MBT expectorator is detected in proper time and is isolated.

Occurrence and course of the infection do not depend only on virulence of the agent, but also on a condition of stability and reactivity of a host.

The site of MBT penetration into the host is most important because at this site there is primary contact between MBT and a host (entrance of infection). The place of MBT penetration into the host is most important because in this site the primary contact between MBT and a host takes place (entrance gates of infection). The following ways of tuberculosis infection: air-born, alimentary (nutritional), contact.

1. Air-born tuberculosis infection.

11MBT are propagated into the air in the form of droplets while coughing , during conversation and sneezing of the patient infected with active tuberculosis. These infected droplets can penetrate into the lungs of a healthy man during inhalation. This type of infection is called as air-droplet infection (Air-born infection). Depending on the force of cough impulses and of droplet sizes, MBT can be dispersed into the air at different distances from the patient, while coughing – at 2 m, and while sneezing – at 9 m. The basic movement of the spitted particles occurs at a distance of 1 m directly in front of the patient.

Dust infection.
There is also another air born tuberculosis infection, which is also importance, known as dust infection. The droplets of tubercular sputum, gather on a floor, dry up and turn into motes. MBT remain alive inside the motes for some time. It is established, that even after 18 days about 1 % of alive bacteria is still present in dried up sputum. During strong movement of air, while sweeping a floor, movement of the people, the motes containing tubercular MBT, rise into the air, and can penetrate into lungs causing infection.

2. Alimentary (nutritional) pass of infection through digestive tracts.

During special experiments on animals it was shown, that much more MBT is needed for infection through alimentary canal in comparison with air-born infection. For infection of the host during respiration, only one or two mycobacterium tuberculosis is needed, but for infection per os hundreds of MBT are needed. The ways of MBT dissemination in a host during alimentary infection by tubercular culture was demonstrated by the results of post-mortem examinations published in connection with judicial process in Luebeck. By a mistake 252 infants at vaccination through feeding with the tubercular culture (Kiel strain) instead of BCG was entered. Owing to infection 68 children had died from tuberculosis and 131 children were ill; 53 children were healthy. During post mortem examinations of 20 died children, it was seen that in most cases , the process was located in the abdominal organs – place of infection. One of the features of this way of infection of infants is frequent defeat of mesenterial lymphatic nodes by tuberculosis. It is necessary to take into consideration, that the MTB penetration into the intestine can occur at swallowing by the lung tuberculosis patients own sputum that is proved by a presence of MBT in significant quantity of stomach flush waters.

3. Contact ways of MBT penetration into the host.

3.1. Cases of infection through conjunctiva of an eye, can be observed in natural conditions among children and adults; and also acute conjunctivitis and inflammation of the lachrymal sac can sometimes be found.

3.2. The infection of the skin during tuberculosis is seldom met. The cases of tuberculosis infected milkmaids are mostly found due to MBT penetration through the injured skin of hands from the cows diseased by tuberculosis. Morbid anatomists, forensic medical examination doctors at examination of corpses also died from tuberculosis. This type of tubercular infection meets seldom.

3.3. Intrauterine tuberculosis infection. The possibility of tuberculosis of the fetus in the intrauterine period was proved on section, of out placental tuberculosis of newborns died in the first days after birth. The infection occurs at tuberculosis lesion of placenta or at affection of injured placenta during delivery by the (tuberculosis) infected mother. This type of tubercular infection meets extremely seldom.

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