What Is Tuberculosis? What Causes Tuberculosis?


Tuberculosis (TB) is an infectious disease that is caused by a bacterium calledMycobacterium tuberculosis. TB primarily affects the lungs, but it can also affect organs in the central nervous system, lymphatic system, and circulatory system among others. The disease was called "consumption" in the past because of the way it would consume from within anyone who became infected.

According to Medilexicon`s medical dictionary, tuberculosis is "A specific disease caused by infection withMycobacterium tuberculosis, the tubercle bacillus, which can affect almost any tissue or organ of the body, the most common site of the disease being the lungs."

When a person becomes infected with tuberculosis, the bacteria in the lungs multiply and cause pneumonia along with chest pain, coughing up blood, and a prolonged cough. In addition, lymph nodes near the heart and lungs become enlarged. As the TB tries to spread to other parts of the body, it is often interrupted by the body's immune system. The immune system forms scar tissue or fibrosis around the TB bacteria, and this helps fight the infection and prevents the disease from spreading throughout the body and to other people. If the body's immune system is unable to fight TB or if the bacteria breaks through the scar tissue, the disease returns to an active state with pneumonia and damage to kidneys, bones, and the meninges that line the spinal cord and brain. 

TB is generally classified as being either latent or active. Latent TB occurs when the bacteria are present in the body, but this state is inactive and presents no symptoms. Latent TB is also not contagious. Active TB is contagious and is the condition that can make you sick with symptoms. 

TB is a major cause of illness and death worldwide, especially in Africa and Asia. Each year the disease kills almost 2 million people. The disease is also prevalent among people with HIV/AIDS.

Global tuberculosis campaign threatened by multi-drug resistance

In October 2012, Dr. Mario Raviglione, Director of the WHO Stop TB Department, warned thatthe number of people becoming infected with MDT-TB (multi-drug-resistant) tuberculosis has risen considerably. He added that too few are being diagnosed and treated.

The global campaign to reduce TB infections by half by 2015 could be seriously jeopardized by MDT-TB.

We are now at a crossroads, Dr. Raviglione emphasized - either we eradicate TB in our lifetime, or the disease becomes increasingly resistant, harder to treat, and gains ground.

In March 2013 WHO, warned about a serious funding shortage. Dr. Margaret Chan, Director-General of WHO warned that without expanded treatment and funding, the global fight against TB will be seriously undermined. Dr. Chang said "We are treading water at a time when we desperately need to scale up our response to MDR-TB. We have gained a lot of ground in TB control through international collaboration, but it can easily be lost if we do not act now."

What causes tuberculosis?

Tuberculosis is ultimately caused by the Mycobacterium tuberculosis that is spread from person to person through airborne particles. It is not guaranteed, though, that you will become infected with TB if you inhale the infected particles. Some people have strong enough immune systems that quickly destroy the bacteria once they enter the body. Others will develop latent TB infection and will carry the bacteria but will not be contagious and will not present symptoms. Still others will become immediately sick and will also be contagious.

What are the symptoms of tuberculosis?

Most people who become infected with the bacteria that cause tuberculosis actually do not present symptoms of the disease. However, when symptoms are present, they include unexplained weight loss, tiredness, fatigue, shortness of breath, fever, night sweats, chills, and a loss of appetite. Symptoms specific to the lungs include coughing that lasts for 3 or more weeks, coughing up blood, chest pain, and pain with breathing or coughing.

How is tuberculosis diagnosed?

Tuberculosis diagnosis usually occurs after a combination of skin, blood, and imaging tests. 

The most common diagnostic test is a simple skin test called the Mantoux test. The Mantoux test consists of a small amount of purified protein derivative (PPD) tuberculin that is injected into the forearm. After 48 to 72 hours, a doctor or nurse looks for a reaction at the injection site; a hard, raised red bump usually indicates a positive test for TB. Blood tests may also be used to determine whether TB is active or latent (inactive), and microscopic sputum analyses or cultures can find TB bacteria in the sputum. 

Chest x-rays and computer tomography (CT) scans are also used to diagnose TB. If the immune system traps the TB bacteria and creates scar tissue, this tissue and the lymph nodes may harden like stone in a calcification process. This results in granuloma (rounded marble-like scars) that often appear on x-rays and CT scans. However, if these scars do not show any evidence of calcium on an x-ray, they can be difficult to distinguish from cancer.

Who gets tuberculosis?

Tuberculosis is spread from person to person through tiny droplets of infected sputum that travel through the air. If an infected person coughs, sneezes, shouts, or spits, bacteria can enter the air and come into contact with uninfected people who breath the bacteria into their lungs. 

Although anyone can become infected with TB, some people are at a higher risk, such as:

  • Those who live with others who have active TB infections
  • Poor or homeless people
  • Foreign-born people who come from countries with endemic TB
  • Older people, nursing home residents, and prison inmates
  • Alcoholics and intravenous drug users
  • Those who suffer from malnutrition
  • Diabetics, cancer patients, and those with HIV/AIDS or other immune system problems
  • Health-care workers
  • Workers in refugee camps or shelters

How is tuberculosis treated?

Treatment for TB depends on the whether the disease is active of latent. If TB is in an inactive state, an antibiotic called isoniazid (INH) is prescribed for six to twelve months. INH is not prescribed to pregnant women, and it can cause side effects such as liver damage and peripheral neuropathy

Active TB is treated with INH as well as drugs such as rifampin, ethambutol, and pyrazinamide. It is also not uncommon for TB patients to receive streptomycin if the disease is extensive. Drug therapies for TB may last many months or even years. 

If a patient has a drug-resistant strain of TB, several drugs in addition to the main four are usually required. In addition, treatment is generally much longer and can require surgery to remove damaged lung tissue. 

The largest barrier to successful treatment is that patients tend to stop taking their medicines because they begin to feel better. It is important to finish medications in order to completely eradicate the TB bacteria from the body.

In December 2012, Sirturo (bedaquiline) was approved as part of a combination therapy for adults with multi-drug resistant TB. According to the FDA, bedaquiline was the first TB drug to be approved in the USA in forty years.

Vitamin C helps destroy drug-resistant tuberculosis

Researchers at Albert Einstein College of Medicine, Yeshiva University, reported in the journalNature Communications (May 2013 issue) that vitamin C, when added to existing TB medications, can shorten treatment duration.

The team say that their finding may change how new TB medications are designed.

The scientists say they had been analyzing how TB bacteria become resistant to a first line drug for TB called isoniazid when they made their surprising discovery.

Team leader, William Jacobs, Jr., Ph.D., explained that they had noticed that the TB bacteria that were resistant to isoniazid were lacking in mycothiol (a molecule). "We hypothesized that TB bacteria that can't make mycothiol might contain more cysteine, an amino acid. So, we predicted that if we added isoniazid and cysteine to isoniazid-sensitive M. tuberculosis in culture, the bacteria would develop resistance. Instead, we ended up killing off the culture - something totally unexpected."

Dr. Jacobs believes that cysteine helps destroy TB bacteria by acting as a reducing agent that elicits the creation of free radicals, which can damage DNA.

Jacobs, said "To test this hypothesis, we repeated the experiment using isoniazid and a different reducing agent - vitamin C. The combination of isoniazid and vitamin C sterilized the M. tuberculosis culture. We were then amazed to discover that vitamin C by itself not only sterilized the drug-susceptible TB, but also sterilized MDR-TB and XDR-TB strains."

How can tuberculosis be prevented?

There is a vaccine available for tuberculosis called the BCG vaccine that is used in several parts of the world where TB is common.This vaccine usually protects children and infants from the disease, but adults can still get TB after being vaccinated as children. 

Better methods of preventing tuberculosis or TB relapses include eating a healthful diet that takes care of your immune system, getting a TB test regularly if you work or live in a high risk environment, and finishing TB medications. To prevent transmitting the disease to others if you are infected, stay home, cover your mouth, and ensure proper ventilation. 


Source..medicalnewstoday


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