Tuberculosis is caused by the bacterium Mycobacterium tuberculosis and primarily affects the lungs, though it can spread to other organs. It spreads through airborne droplets when people with active TB cough, sneeze or spit. Diagnosis involves chest x-rays and sputum cultures. Treatment requires a combination of antibiotics over a period of 6-24 months depending on whether the infection is latent or active. The only available vaccine is BCG.

1. Tuberculosis (TB)
Tuberculosis (TB) is a chronic granulomatous
inflammation caused by Mycobacterium tuberculosis.
Tuberculosis generally affects the lungs (known as
pulmonary tuberculosis), but can also affect other
parts of the body such as the CNS, genitourinary tract
and bones (known collectively as extra-pulmonary
tuberculosis).
Fig. 1
M. Tuberculosis

2. Disease spread, incubation and
activeness.
• When people with active pulmonary TB cough, sneeze, speak, sing, or
spit, they expel infectious droplets of saliva. Each one of these
droplets may transmit the disease, since the virulence of tuberculosis
is very high (only 10 bacteria are needed to start an infection)
• The incubation period may vary from about two to 12 weeks
• About 90% of those infected with M. tuberculosis have
asymptomatic, latent TB infections with only a 10% chance the
disease will become active.
• However, people with HIV have an increased 10% chance of
developing the disease each year. (Opportunistic infection)
• Mortality rate for TB is over 50%.

3. Fig. 2
A sneeze.
Showing how
many droplets
are released
(over 40,000).

4. Diagnosis of TB.
Active infection.
Diagnosing active tuberculosis based only on signs
and symptoms is difficult.
A chest X-ray and multiple sputum cultures for acid-
fast bacilli are typically part of the initial evaluation
and can provide definitive evidence of an infection.
Latent infection.
The Mantoux tuberculin skin test is often used to
screen people at high risk for TB

5. Signs and symptoms.
• If a tuberculosis infection does become active, it most commonly
involves the lungs (in about 90% of cases). Symptoms may include chest
pain and a prolonged cough producing sputum. TB also causes caseous
necrosis in the lungs.
• About 25% of people may not have any symptoms (i.e. they remain
"asymptomatic").
• Tuberculosis may become a chronic illness and cause extensive scarring
in the upper lobes of the lungs.
• When a TB infection spreads to other locations besides the lung (via
blood vessels), they are termed extra-pulmonary tuberculosis (or
systemic miliary TB), and they include:
1. Pleura (in tuberculous pleurisy).
2. The CNS (in tuberculous meningitis).
3. The lymphatic system (in scrofula of the neck).
4. The genitourinary system (in urogenital tuberculosis).
5. The bones and joints (in Pott disease of the spine).
6. Others (discussed in the next slide).

7. Fig. 3
Tuberculosis
granulomas.

8. Treatment.
• Treatment of TB uses antibiotics to kill the bacteria.
• Latent TB is treated with either isoniazid alone, or a combination of
isoniazid with rifampicin.
• The recommended treatment of new-onset (active) pulmonary
tuberculosis, is six months of a combination of antibiotics containing
rifampicin, isoniazid, pyrazinamide, and ethambutol.
• Sometimes, the strain of TB bacteria causing the disease may be drug-
resistant. In those cases, combinations of up to 4 drugs need to be used for
at least 18 to 24 months.

9. Prevention of TB.
A. Vaccines
The only available vaccine as of 2011 is Bacillus Calmette-Guérin (BCG).
In children it decreases the risk of getting the infection by 20% and the
risk of infection turning into active disease by nearly 60%.
B. Campaigns and public education on the prevention of the spread of
the disease by WHO or other government/non-government
organizations have had some success in reducing the spread of the
disease.

10. Fig. 4
Tuberculosis prevention poster
from the United States.
Fig. 5
Public health campaigns in the 1920s
tried to halt the spread of TB.