Tuberculosis

Definition of Tuberculosis
Tuberculosis is a chronic infection caused by the bacteria Mycobacterium tuberculosis (and occasionally other variants of Mycobacterium). It usually involves the lungs, but other organs of the body can also be involved.
Tuberculosis Causes
All cases of TB are passed from person to person via droplets. When someone with TB infection coughs, sneezes, or talks, tiny droplets of saliva or mucus are expelled into the air, which could be inhaled by another person.
Once infectious particles reach the alveoli, small sacs in your lungs, another cell called the macrophage engulfs the TB bacteria.
Then the bacteria are transmitted to your lymph system and bloodstream and spread to other organs.
The bacteria further multiply in organs that have high oxygen pressures, such as the upper lobes of your lungs, your kidneys, bone marrow, and meninges—the membranelike coverings of your brain and spinal cord.

When the bacteria cause clinically detectable disease, you have TB.
People who have inhaled the TB bacteria, but in whom the disease is controlled are referred to as infected. They have no symptoms, frequently have a positive skin test, yet cannot transmit the disease to others.
Risk factors for TB include the following:
HIV infection
Low socioeconomic status
Alcoholism
Homelessness
Crowded living conditions
Diseases that weaken the immune system
Migration from a country with a high number of cases
Health care workers
Tuberculosis Symptoms
You may not notice any symptoms of illness until the disease is quite advanced. Even then the symptoms–loss of weight, loss of energy, poor appetite, fever, a productive cough, and night sweats–might easily be blamed on another disease.
Only about 10% of people infected with M tuberculosis ever develop tuberculosis disease. Many of those who suffer TB do so in the first few years following infection, but the bacillus may lie dormant in the body for decades.
Although most initial infections have no symptoms and people overcome them, they may develop fever, dry cough, and chest x-ray abnormalities.
This is called primary pulmonary tuberculosis.
Pulmonary tuberculosis frequently goes away by itself, but in 50-60% of cases the disease can return.

Tuberculous pleuritis may occur in 10% of people who have the lung disease from tuberculosis.
The pleural disease occurs from the rupture of a diseased area into the pleural space, the space between your lung and the lining of the abdominal cavity.
These people have a nonproductive cough, chest pain, and fever. The disease may go away and then come back at a later date.

In a minority of people with weakened immune systems, TB bacteria may spread through their blood to various parts of their body.
This is called miliary tuberculosis and produces fever, weakness, loss of appetite, and weight loss.
Cough and difficulty breathing are less common.

Generally, return of dormant tuberculosis infection occurs in the upper lungs.
Common cough with a progressive increase in production of mucus
Coughing up blood
Other symptoms include the following:
Fever
Loss of appetite
Weight loss
Night sweats

About 15% of people may develop tuberculosis in an organ other than their lungs. About 25% of these people usually had known TB with inadequate treatment. The most common sites include the following:
Lymph nodes
Genitourinary tract
Bone and joint sites
Meninges
The lining covering the outside of the gastrointestinal tract
Exams and Tests
The doctor will complete the following tests to diagnose tuberculosis. You may not be hospitalized for either the initial tests or the beginning of treatment.
Chest x-ray: The most common diagnostic test that leads to the suspicion of infection is a chest x-ray.
In primary TB an x-ray will show an abnormality in your mid and lower lung fields, and lymph nodes may be enlarged.
Reactivated TB bacteria infiltrate the upper lobes of your lungs.
Miliary tuberculosis exhibits diffuse nodules.

Mantoux skin test: This test helps identify people infected with M tuberculosis but who have no symptoms. A doctor must read the test.
The doctor will inject 5 units of purified protein derivative (PPD) into your skin. If a raised bump of more than 5 mm (0.2 in) appears at the site 48 hours later, the test may be positive.
This test can often indicate disease when there is none (false positive). Also, it can show no disease when you may in fact have TB (false negative).

Sputum testing: Sputum testing for acid-fast bacilli is the only test that confirms a TB diagnosis. If sputum (the mucus you cough up) is available, or can be induced, a lab test may give a positive result in up to 30% of people with active disease.
Sputum or other bodily secretions such as from your stomach or lung fluid can be cultured for growth of mycobacteria to confirm the diagnosis.
It may take 1-3 weeks to detect growth, but 8-12 weeks to be certain
Tuberculosis Treatment
Medical Treatment
Today, doctors treat most people with TB outside the hospital. Gone are the days of going to the mountains for long periods of bed rest. Doctors seldom use surgery.
Doctors will prescribe several special medications that you must take for 6-9 months.
Standard therapy for active TB consists of a 6-month regimen:
2 months with Rifater (isoniazid, rifampin, and pyrazinamide)
4 months of isoniazid and rifampin (Rifamate, Rimactane)
Ethambutol (Myambutol) or streptomycin added until your drug sensitivity is known

Treatment takes that long because the disease organisms grow very slowly and, unfortunately, also die very slowly.
Doctors use multiple drugs to reduce the likelihood of resistant organisms emerging.
Often the drugs will be changed or chosen based on the laboratory results.
If doctors doubt that you are taking your medicine, they may have you come to the office for doses. Prescribing doses twice a week helps assure compliance.
The most common cause of treatment failure is people's failure to comply with the medical regimen. This may lead to the emergence of drug-resistant organisms. You must take your medications as directed, even if you are feeling better.

Another important aspect of tuberculosis treatment is public health.
Doctors likely will contact or trace your relatives and friends.
Your relatives and friends may need to undergo appropriate skin tests and chest x-rays.
Prevention
Treatment to prevent TB in a single person aims to kill walled-up germs that are doing no damage right now, but could break out years from now and become active.
If you should be treated to prevent sickness, your doctor usually prescribes a daily dose of isoniazid (also called INH), an inexpensive TB medicine.
You will take INH for up to a year, with periodic checkups to make sure you are taking it as prescribed and that it is not causing undesirable side effects.

Treatment also can stop the spread of TB in large populations.
Tuberculosis vaccine, known as bacille Calmette-Guérin (BCG) may prevent the spread of tuberculosis and tuberculous meningitis in children, but the vaccine does not necessarily protect against pulmonary tuberculosis.
Health officials generally recommend the vaccine in countries or communities where the rate of new infection is greater than 1% per year.