Tuberculosis

Tuberculosis. Overview

Tuberculosis is an infectious disease typically caused by small aerobic bacteria called Mycobacterium tuberculosis. There are several other mycobacteria that can cause this disease but they are quite rare. Some of them are spread only in certain areas in Africa, one of species is observed almost only in immunodeficient people.

In 80-85% of cases tuberculosis occurs in the lungs, being called pulmonary tuberculosis. But it can also occur in other parts of the body, including pleura, the central nervous system, the lymphatic system, the genitourinary system, the bones and joints. This type of disease is called extrapulmonary tuberculosis, it typically occurs in immunosuppressed patients and young children (M. P. Golden, H. R. Vikram. Extrapulmonary tuberculosis: an overview. American Family Physician. 2005, November, 72 (9): 1761–68).

There are many cases of latent tuberculosis infection, when a person is infected by mycobacteria but does not develop active form of disease. People with latent tuberculosis are non-contagious, however, these people have a big risk of progressing into active form. In active form, Mycobacterium tuberculosis bacteria fights with the host’s immune cells, eventually kills them and results in death of the host in 50% of cases when left untreated.

More than 90% of children in developed countries are vaccinated by Bacillus Calmette-Guerin (BCG) vaccine. It significantly decreases the risk of getting infected. But after about ten years immunity starts to decrease and the vaccine does not guarantee a life-long protection.

Symptoms of tuberculosis

Active form of pulmonary tuberculosis:

• chronic cough
• cough with blood-containing mucus,
• chest pain,
• fatigue,
• fever,
• chills,
• night sweats,
• poor appetite,
• weight loss
• nail clubbing.

Latent form of tuberculosis:

Unfortunately, there are almost no symptoms showing the person got infected with mycobacteria unless laboratory tests are provided. Screening with tuberculin skin tests or interferon-gamma tests can help to detect the disease at an earlier stage.

Extrapulmonary tuberculosis:

Extrapulmonary tuberculosis can cause various symptoms depending on location of the disease. Gastrointestinal symptoms, fever, weakness and poor appetite are the most common. Extrapulmonary tuberculosis can coexist with a pulmonary form.

Causes of tuberculosis

Tuberculosis is spread by the persons with the disease in active form speaking, singing, coughing, sneezing or spitting. The disease is highly contagious, inhaling less than 10 bacteria is enough to get infected. The risk is particularly high for people who have prolonged, close or frequent contact with patients with active form. The risk also depends on several factors, such as: the frequency and the duration of the exposure, the virulence of the particular mycobacteria strain, the effectiveness of the ventilation and others. Smoking and having low level of immunity also increase the risk (patients with HIV or AIDS are highly likely to get infected).

Tuberculosis Treatment Methods

Unfortunately, at current moment, there is no 100% cure for tuberculosis. First step to the treatment is a timely diagnostic, especially for people in the risk group. Mycobacteria has a very unusual structure and chemical composition of the cell wall, that make many of the antibiotics ineffective. Also, mycobacteria have an ability to develop the antibiotic resistance. That’s why the treatment usually consists of several antibiotics combined together and used from 3 to 9 months for active form of tuberculosis. These antibiotics include:

• isoniazid,
• rifampicin/rifampin,
• pyrazinamide,
• ethambutol,
• streptomycin or kanamycin.

For latent form of tuberculosis most of specialists recommend a treatment course of isoniazid and regular screening in order to prevent developing an active form.