The whole truth about TB | Print |
Tuberculosis: pathogen, pathogenesis, risk of disease, epidemiology.

Causative agent of tuberculosis
In 2012, March 24 marks 130 years since this discovery by R.Koch pathogen, called tuberculosis (Latin tuberculum - bump), since the post mortem examination of the dead bodies were found in the lungs of patients with lesions ("bumps") often with the deposition lime. The opening of the pathogen was conclusive evidence of the infectious nature of TB.
Mycobacterium tuberculosis (MBT) is a representative of a large group of mycobacteria related lower plant organisms - radiant fungi (actinomycetes). In pathological material Mycobacterium tuberculosis have the form of thin, slightly curved, homogeneous or granular rods in length from 1 to 10 mm and a width of 0.2 to 0.6 microns.
Mycobacterium tuberculosis - an aerobic organism. The optimum temperature for it 38?, PH 6.8-7.2 environment. It grows well in media containing egg, milk, potatoes, glycerine, but slowly: first colonies appear on the 10-30th day, and sometimes after 1.5 months.
The main characteristic that relate to the ILO or other kind, is a variety of pathogenic them for different types of animals and humans. Human pathogenic mycobacteria are of the human species (M.tuberculosis) in 92% of the bovine (M.bovis) in 5% of cases and an intermediate form (M.africanum) in 3% of cases.
Mycobacterium tuberculosis resistant to various environmental factors. In the soil, water, and living areas, in certain foods (milk, butter, cheese) bacteria remain viable for about a year in the books - up to 3 months, street dust - up to 8-12 days in water - up to 5 months . Characteristic resistance to acids, alkalis, alcohols. Direct sunlight and ultraviolet rays kill the Office within a few minutes, they are destroyed by boiling in 45 minutes. In vitro culture of mycobacteria may be maintained without subculture up to 1 year, and in the frozen state remain viable up to 30 years.
In recent years, the disease register, called mycobacteriosis caused by atypical (non-tuberculous) mycobacteria, which was combined with the ILO factor is the acid resistance.
A characteristic feature of M. tuberculosis is its ability to develop resistance to anti-TB drugs. More often than not - is the result of inadequate chemotherapy, the use of improper treatment regimens by combination and dosage, duration of treatment and patient compliance to treatment. The Office considered stable that retain the ability to grow at certain concentrations of anti-tuberculosis drugs in the culture medium. Bacteriological population ILO considered resistant if one or more percentage of bacteria resistant to certain concentrations.
The following types of drug resistance (DR) of Mycobacterium tuberculosis to antituberculosis drugs:
- Monorezistentnost (LU-to-one anti-TB drug);
- Multi-drug resistant (MDR) or multiresistance to two or more drugs, if two of them are isoniazid and rifampicin;
- Polyresistance to which the other cases of resistance to two or more drugs, if not one of them at the same time a combination of isoniazid and rifampicin;
- Extensively drug-resistant (XDR) - a multiple drug resistance in combination with resistance to fluoroquinolone, and to at least one of three injectable second-line drugs (kanamycin, amikacin, capreomycin).
Distinguish between primary and acquired (secondary) drug resistance. Primary LU diagnosed in patients who have not previously received anti-TB drugs, or been treated for less than 1 month, ie These patients already infected with resistant mycobacteria. Acquired or secondary drug resistance is detected in TB patients who received previous treatment with anti-TB drugs.
Level of the primary LU is a reflection of the level of acquired DR in the population and is directly dependent on it. The more patients that produce resistance of MBT, the greater the risk of transmission of resistant MBT healthy people and the emergence of new TB cases with primary resistance. Therefore, the primary indicator of DR MBT with epidemiological position reflects not only the general situation with the detection and treatment of tuberculosis, but the degree of isolation MbT and sanitary aspects of prevention. LU primary indicator provides a measure of strength of the epidemiological situation of tuberculosis in a given region.
Thanks to the advances in molecular epidemiology of tuberculosis, which studies the structure of DNA Office, it became possible to judge the genetic relationship of mycobacterial strains isolated from patients. Using laboratory techniques of molecular study bacterial DNA positive patients previously obtained data on the genetic identity of only 17% of cases. Thus, we have proved a serious role of exogenous infection in the epidemiology of tuberculosis. Of molecular epidemiology also showed that distributors may be patients of tuberculosis in sputum smears which the Office is not detected. They become a source of transmission of tuberculosis in one fifth of the disease.
To infect the body's Office, and in the future and the possible development of the disease, you need contact with the tuberculosis infection, most often with a person suffering from infectious tuberculosis. The risk of infection is directly proportional to the duration of exposure.
The source of infection - is Typhoid Mary, which selects the Office to the surrounding air by coughing, sneezing, talking, etc. Particular risk factor of infection is coughing, is 5 minutes of loud conversation. The risk of infection (contact agent) significantly increased in contact between two people close enough to keep the conversation between the two, or in a confined space where ventilation (ventilation) was insufficient. In an average year one infectious TB patient can infect 15-20 susceptible to infection people.
In the 30-ies of XX century, Wells found cultivated air of the ILO, preserved in the form of small particles, which penetrate deep breathing into the lungs. The diameter of the smallest drops containing infection, called infectious aerosols is 1-3 microns. Average sedimentation rate of the aerosol diameter of 1 cm / min.
In the 60's of last century, a group established Luodona life expectancy aerosol Office about 6 hours. Large respiratory particles dispersed within one meter from its source and easily adhere to the surface. Fine particles in the transport of air drying of sources, and can travel over long distances through the ventilation system. Thus, the causative agent of tuberculosis spreads aerogenic by, not airborne, as was previously thought.
Infection occurs when a small bronchi to the alveoli of human lungs susceptible to infection with the inhaled air enters the infectious aerosol containing the ILO, which is integrated in the lung tissue, can form the primary site of disease. Dose of bacteria that lead to human infection with tuberculosis, are small: 1-10 of bacteria that may be present in 1-3 aerosol particles. Clinical symptoms may appear soon after infection, but usually the immune response triggered within 2-10 weeks, which hinders the further reproduction and distribution of the ILO.
Ways of nosocomial spread of tuberculosis infection:
Patient Paramedic
Paramedic Patient
Patient Patient
The most dangerous way of nosocomial transmission of tuberculosis - a professional health care provider the risk of infection from the patient, as well as work with the pathological material.
At increased risk are those health workers who often and longer than any other direct contact with patients, have a long record of service, contact with TB patients has not yet undergone diagnosis and begin treatment, working in health care organizations that are not qualified and in full volume carried out to infection control; teach patients how to properly collect and expectorate sputum.
According to WHO, the highest risk of transmission of TB occurs in prisons and brief detention. High burden of TB in prisons is due not finding diagnosed cases in crowded indoor teams at failure of infection control measures.
Patients with drug-sensitive releasing Office, cease to be dangerous in the transmission of infections within 2-3 weeks after the start of effective TB therapy. When LU forms of tuberculosis sputum duration increases. These patients are a source of infection for a much longer period of time after the start of effective TB therapy.
Maximum risk of nosocomial transmission of infection occurs when patients have not been diagnostic phase and do not receive treatment. Therefore, the key to reducing the risk of nosocomial spread of TB is early diagnosis and early treatment of patients.
Most infections in laboratory services for diagnosis and monitoring of TB chemotherapy is due to underestimation of the danger of infectious aerosols containing Office.
Nutritional risk of tuberculosis infection in the laboratory occurs when infectious material ingested by sucking in contaminated liquid dropper or entered into the mouth infected hands. Hands can be contaminated not only inside the box, but the outer surface of the container for sputum. It is recommended to work with containers in gloves to treat the outer surface of the container and wash hands frequently.
Infection can occur when pricked with a needle contaminated with the Office, or blood infected with HIV or hepatitis viruses parenteral as tuberculosis are often infected with HIV and hepatitis viruses parenteral. In this connection, it is necessary to pay attention not only to minimize the possible infection of laboratory TB, but to prevent possible infection with HIV and hepatitis.
To prevent infection it is recommended not to use syringes with needles instead of pipettes, avoid cuts destroyed edge of glassware or pipettes. Do not use battered dishes. If possible, the glassware should replace plastic. All procedures with infected material in the microbiology laboratory should be done only with rubber gloves.

Pathogenesis of Tuberculosis
The most common way of TB - aerogenic, but possible and nutritional and rarely - contact through broken skin or mucous membranes. Of all the organs and systems of the body most often affects the lungs, where the introduction of infection in tuberculosis formed inflammatory center described Ghosn (1912). Simultaneously tuberculous inflammation develops in the hilar lymph nodes. Only in few cases, the primary infection, and it is often children and youth, develop TB disease (primary TB). Typically, the inflammatory process is completely absorbed in his place or form dense foci with elements of lime (calcifications, petrifikaty). Man remains healthy. Being infected, people like to become resistant to repeated infiltration of mycobacteria, ie formed immunity. Acquired immunity in tuberculosis, unfortunately, are unstable and maintained macroorganism conservation of living virulent ILO stalled primary foci petrifikatah, lymph nodes.
Time become the primary TB infection can be established by setting the Mantoux tuberculin skin test. Its positive result in this case is called the "turn" tuberculin skin test.
Support TB immunity incorporated into a vaccine strain, opened by French scientists Calmette, Guerin (1914) and called their name (BCG - Bactlles Calmette, Guerin), which is a harmless preparation of live attenuated vaccine strain of Mycobacterium tuberculosis BCG.
When infecting a vaccinated person virulent Office last multiply very slowly, losing a tendency to spread, are blocked at the injection site, and the disease does not occur, and if they develop active tuberculosis process, it takes a more benign and quickly cured.
Secondary tuberculosis develops as a result of endogenous reactivation of tuberculosis or re-infection with Mycobacterium tuberculosis (exogenous pathway).
Morphological picture of tuberculous focus of inflammation is characterized by epithelioid and giant cells Pirogov-Langhans, and in the center - the formation of cheesy necrosis (caseation). In difficult diagnostic cases, the morphological picture of the biopsy material obtained from the patient, it is the only way to verify the clinical diagnosis of tuberculosis.
ICD-10 TB assigned to Class I "Certain infectious and parasitic diseases" (A15-A19), where A15-pulmonary tuberculosis, confirmed bacteriologically and histologically, A16 - pulmonary tuberculosis, not confirmed bacteriologically or histologically, A17 - TB nervous system A18 - tuberculosis of other organs, A19 - miliary tuberculosis.
According to the clinical classification of tuberculosis, approved by the Ministry of Health of the Republic of Belarus "On additional measures to strengthen TB control in the country" from 06.12.1996 № 266 pulmonary tuberculosis has the following clinical forms: primary tuberculosis complex, tuberculosis of intrathoracic lymph nodes, disseminated, focal , infiltrative, cavernous, cavernous fibrosis, cirrhotic, pulmonary tuberculosis, miliary tuberculosis, caseous pneumonia, pulmonary tuberculoma, tuberculous pleurisy, tuberculosis, bronchial tubes, trachea, upper respiratory tract, as well as combined with dust related occupational lung diseases. Tuberculosis of other organs and systems, including tuberculosis of the meninges and central nervous system, intestines, peritoneum and mesenteric lymph nodes, bones and joints, urinary, reproductive organs, skin and subcutaneous tissue, lymph nodes, eyes, other organs.

The risk of tuberculosis
For pulmonary tuberculosis and other sites no pathognomonic symptoms. TB can often be asymptomatic and diagnosed during regular checkups population. At the same time, the patient's complaints to prolonged cough (more than 3 weeks), chest pain, blood in sputum, weight loss in the normal diet, loss of appetite, increased sweating (especially at night), malaise, and weakness , periodic fever should show caution, especially in the absence of non-specific effects of the treatment of broncho-pulmonary disease.
Extrapulmonary tuberculosis symptoms associated with specific organs affected are: lymph nodes, pleura, larynx, meninges, urinary and gastrointestinal tracts, bones, spine, skin and eyes.
Tuberculosis can hurt anyone, but the public release of people who have an increased risk of tuberculosis because of their social and / or medical specialties. It is "endangered" (in tuberculosis) contributors whose risk of tuberculosis in five or more times higher than among the general population. As practice shows, among new TB patients, more than 85% can be classified as "threatened" contingents.
Social risk "endangered" (in tuberculosis) contingents are:
unemployed registered at employment centers;
homeless persons, refugees and migrants;
persons released from institutions of the executive system, after arriving for permanent residence;
persons residing in institutions of social services (shelters, shelters, for the elderly, etc.), and people with disabilities;
persons with chronic alcoholism and drug addiction;
persons discharged from LTP;
soldier, military service.