Thursday, May 15, 2008



What is TB (tuberculosis infection)?

TB or tuberculosis is a disease caused by a bacterium called Mycobacterium tuberculosis. Mycobacterium tuberculosis belongs to the sub group mycobacterium tuberculosis complex, in this group there are other members, and of notice are- (M. bovis, M. Africanum and M. bovis BCG). The bacteria can attack any part of the body, usually affecting the lungs (pulmonary TB). Other parts of the body can also be affected, for example lymph nodes, kidneys, bones, joints, etc. (extra pulmonary TB).

How TB Spread (route of transmission):

The TB’s primary route of transmission is through person to person by inhalation of droplet nuclei that contain the organism (infectious aerosols, 1-5um) that are produced when infected individuals with pulmonary TB cough, sneeze, speak, or sing; infectious aerosols maybe also produced by manipulations of lesions or processing clinical specimens in the laboratory. The droplets are so small that the air currents keep them air-borne for long periods of time and once inhaled, they are small enough to reach the lung’s alveoli.

TB in other parts of the body, such as the kidney or spine, is usually not infectious. People with TB disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers.

Signs and symptoms:

TB may mimic other diseases such as pneumonia, neoplasm, or fungal infections. In addition, clinical manifestations of patients infected with TB complex may range from asymptomatic to acutely symptomatic. Patients who are asymptomatic can still have systemic symptoms, pulmonary signs and symptoms and signs and symptoms that are related to other organ involvement (e.g., kidney) or a combination of these features. Of note, cases of pulmonary disease caused by M.tuberculosis complex organisms are clinically, radiologically and pathologically indistinguishable.

Common presenting signs and symptoms:

TB mainly affects the lungs (pulmonary tuberculosis), and coughing is often the only indication of infection initially.

Signs and symptoms of active pulmonary TB include:

A cough lasting three or more weeks that may produce discolored or bloody sputum (normally referred to as positive sputum) Unintended weight loss, Fatigue, Slight fever (low-grade fever), Loss of appetite(anorexia), Pain with breathing or coughing (pleurisy). Tuberculosis also can target almost any part of your body, including your joints, bones, urinary tract, central nervous system, muscles, bone marrow and lymphatic system.

When TB occurs outside your lungs, signs and symptoms vary, depending on the organs involved. For example, tuberculosis of the spine may result in back pain, and tuberculosis that affects your kidneys might cause blood in your urine. Tuberculosis can also spread through your entire body, simultaneously attacking many organ systems. It should be noted that immunocompromised patients i.e. the elderly and more so individuals infected with HIV are particularly susceptible to developing active TB. They are more likely to have rapidly progressive primary disease instead of the sub clinical infection. Of further concern is the diagnosis of TB which becomes more difficult in persons with HIV, because the chest radiographs of pulmonary disease often lack specificity and frequently the patients are allergic to tuberculin skin testing, a primary means to identify individuals infected with TB. The TB test or PPD (purified protein derivative) test is based on the premise that following infection with M.tuberculosis, a patient will develop a delayed hypersensitivity cell-mediated immunity to certain antigenic components of the organism. To determine whether a person has been infected with M.tuberculosis, a culture extract of M.tuberculosis (i.e. PPD of tuberculin) is intravenously injected. After 48-72 hours, a person who has been infected will exhibit a delayed hypersensitivity reaction to the PPD; this reaction is characterized by erythema (redness) and most important, induration (firmness as a result of influx of immune cells). The diameter of induration is measured and then interpreted as whether the patient has been infected or not. Different criteria exist for different patient populations (e.g., immunosuppresed persons, such as those infected with HIV). It is also important to bear in mind that the test is not 100% sensitive or specific, and positive reaction to the skin does not necessarily signify the presence of the disease.


Treating TB infection (asymptomatic)

If tests show that you have TB infection but not active disease, your doctor may recommend preventive drug therapy to destroy dormant bacteria that might become active in the future. In that case, you're likely to receive a daily dose of the TB medication isoniazid (INH). For treatment to be effective, you usually take INH for six to nine months. Long-term use can cause side effects, including liver disease-hepatitis. For that reason, your doctor will monitor you closely while you're taking INH. During treatment, avoid using acetaminophen (Tylenol, others) and avoid or limit alcohol use. Both greatly increase your risk of liver damage.

Treating active TB disease (symptomatic)

If you're diagnosed with active TB, you're likely to begin taking four medications - isoniazid, rifampin (Rifadin, Rimactane), ethambutol (Myambutol) and pyrazinamide. This regimen may change if susceptibility tests later show some of these drugs to be ineffective. Even so, you'll continue to take several medications. Depending on the severity of your disease and whether there is drug resistance, one or two of the four drugs may be stopped after a few months. Sometimes the drugs may be combined in a single tablet such as Rifater, which contains isoniazid, rifampin and pyrazinamide. This makes your therapy less complicated while ensuring that you get the different drugs needed to completely destroy TB bacteria. Another drug that may make treatment easier is rifapentine (Priftin), which is taken just once a week during the last four months of therapy. Sometimes you may be hospitalized for the first two weeks of therapy or until tests show that you're no longer contagious. Completing treatment is essential.

Because TB bacteria grow slowly; treatment for an active infection is lengthy - usually six to 12 months. After a few weeks, you won't be contagious and may start to feel better, but it's essential that you finish the full course of therapy and take the medications exactly as prescribed by your doctor. Stopping treatment too soon or skipping doses can create drug-resistant strains of the disease that are much more dangerous and difficult to treat. Drug-resistant strains that aren't treated can quickly become fatal, especially in people with impaired immune systems. In an effort to help people stick with their treatment regimen, some doctors and clinics use a program called directly observed therapy short-course (DOTS). In this approach, a nurse or other health care professional administers your medication so that you don't have to remember to take it on your own.

Treatment side effects:

Side effects of TB drugs aren't common, but can be serious when they do occur. All TB medications can be highly toxic to your liver. Rifampin can also cause severe flu-like signs and symptoms - fever, chills, muscle pain, nausea and vomiting. When taking these medications, call your doctor immediately if you experience any of the following:

Nausea or vomiting, Loss of appetite, A yellow color to your skin (jaundice), A fever lasting three or more days that has no obvious cause, such as a cold or the flu, Tenderness or soreness in your abdomen, Blurred vision or colorblindness.

Treating drug-resistant TB:

Multi-drug-resistant TB (MDR-TB) is any strain of TB that can't be treated by the two most powerful TB drugs, isoniazid and rifampin. Extensive drug-resistant TB (XDR-TB) is a newly developed strain of TB that's resistant to the same treatments that MDR-TB is, and additionally XDR-TB is resistant to three or more of the second-line TB drugs. Both strains develop as a result of partial or incomplete treatment - either because people skip doses or don't finish their entire course of medication or because they're given the wrong treatment regimen. This gives bacteria time to undergo mutations that can resist treatment with first-line TB drugs. MDR-TB can be treated. But it requires at least two years of therapy with second-line medications that can be highly toxic. Even with treatment, many people with MDR-TB may not survive.

And when treatment is successful, people with this form of TB may need surgery to remove areas of persistent infection or repair lung damage. Treating these resistant forms of TB is far more costly than treating nonresistant TB, making therapy unaffordable in many parts of the world. Because these resistant infections are spreading and could potentially make all TB incurable, some experts believe that ineffective treatment is ultimately worse than no treatment at all.

Treating people who have HIV/AIDS:

Treating people who are co-infected with TB and HIV is a particular challenge. HIV-positive people are especially likely to develop MDR-TB and to rapidly progress from latent to active infection. What's more, the most powerful AIDS drugs - protease inhibitors - interact with rifampin and other drugs used to treat TB, reducing the effectiveness of both types of medications. To avoid interactions, people living with both HIV and TB may stop taking protease inhibitors while they complete a short course of TB therapy that includes rifampin. Or they may be treated with a TB regimen in which rifampin is replaced with another drug that's less likely to interfere with AIDS medications. In such cases, doctors carefully monitor the response to therapy, and the duration and type of regimen may change over time. Without treatment, most people living with both HIV and TB will die, often in a matter of months. In such cases, the primary cause of death is TB, not AIDS.


In general, TB is a preventable disease. From a public health standpoint, the best way to control TB is to diagnose and treat people with TB infection before they develop active disease and to take careful precautions with people hospitalized with TB. But there are also measures you can take on your own to help protect yourself and others:Keep your immune system healthy. Make sure you eat plenty of healthy foods, get adequate amounts of sleep and exercise regularly to keep your immune system in top form.Get tested regularly. Experts advise getting a skin test annually if you have HIV or another disease that weakens your immune system, live or work in a prison or nursing home, are a health care worker, or have a substantially increased risk of exposure to the disease.Consider preventive therapy. If you test positive for latent TB infection, but have no evidence of active TB, talk to your doctor about therapy with isoniazid to reduce your risk of developing active TB in the future. A vaccine, BCG, is available and has been of some benefit in preventing TB. It is more commonly administered in countries where TB is more common. The vaccine isn't very effective in adults, although it can prevent TB from spreading outside the lungs in infants. Vaccination with BCG also causes a false-positive result on a Mantoux skin test and for that reason, isn't recommended for general use in some countries like US.

Researchers are working on developing a more effective TB vaccine. Either way, finish your entire course of medication. This is the most important step you can take to protect yourself and others from TB. When you stop treatment early or skip doses, TB bacteria have a chance to develop mutations that are resistant to the most potent TB drugs. The resulting drug-resistant strains are much more deadly and difficult to treat.

To help keep your family and friends from getting infected if you have active TB:

Stay home. Don't go to work or school or sleep in a room with other people during the first few weeks of treatment for active TB. Ensure adequate ventilation. Open the windows whenever possible to let in fresh air. Cover your mouth. It takes two to three weeks of treatment before you're no longer contagious. During that time, be sure to cover your mouth with a tissue any time you laugh, sneeze or cough. Put the dirty tissue in a bag, seal it and throw it away. Also, wearing a mask when you're around other people during the first three weeks of treatment may help lessen the risk of transmission.

Coping skills:

Undergoing treatment for TB for a long period of time can be complicated, yet sticking with therapy is the only way to cure the disease. You may find it helpful to have your medication administered by a nurse or other health care professional so that you don't have to remember to take it on your own. In addition, try to maintain your normal activities and hobbies and stay connected with family and friends. Keep in mind that your physical health can directly impact your mental health. Denial, anger and frustration are not uncommon when you learn life has dealt you something difficult and unexpected. At times, you may need more tools to deal with these or other emotions. Professionals, such as therapists or behavioral psychologists, may help you put things in perspective.

No comments: