Tuberculosis (TB) is a bacterial infection of the lungs, which is caused by the microorganism Mycobacterium tuberculosis. Symptoms may include cough, shortness of breath, pleurisy (inflamed membranes around the lungs), fever, weight loss, night sweats, chills and loss of appetite. The disease can cause serious respiratory problems, which can be life threatening, especially if left untreated.
Tuberculosis is transmitted through airborne droplets. People become infected with TB when they inhale particles of infected sputum from the air. The bacteria become airborne when an infected person expels saliva (when they cough, sneeze, talk, spit, etc.).
About 10 to 15 million Americans have latent TB infections, which means they do not express any symptoms of TB, but they carry the bacterium that causes the disease. These individuals have healthy immune systems that are able to suppress the infection. Only 10% of individuals with latent TB develop the infection.
However, patients who have weakened immune systems, including HIV patients, have an increased risk of developing active TB infections. The risk of developing active TB increases 7-10% in HIV patients who have latent TB. Since HIV patients are immunocompromised, they are more likely to experience symptoms in areas of the body other than the lungs (extrapulmonary TB) than the general population. The disease may affect the bones, joints, nervous system or urinary tract. Also, TB appears to make HIV infection worse.
In 2003, about 11 million people worldwide (nine percent in the United States) were infected with both HIV and TB. Tuberculosis is the leading cause of death among HIV-positive individuals, accounting for 13% of AIDS deaths worldwide. However, in the United States, tuberculosis is a much less common cause of death in HIV/AIDS patients.
HIV-infected patients who have TB usually recover from TB if treatment is started early. Antibiotics are typically prescribed for six to 12 months. The exact drugs and length of treatment varies, depending on the patient's age, overall health and state of the disease (latent or active).
HIV-infected patients are encouraged to have a tuberculin test (TB skin test) each year. If the test is positive, TB is highly suspected. The test cannot determine whether the infection is active or inactive. It also cannot tell the difference between a TB infection and a TB vaccination. Therefore, additional tests, such as a chest X-ray, a sputum culture or both, are usually performed to determine whether the patient has an active TB infection.
Mycobacterium tuberculosis causes tuberculosis. This microscopic organism primarily attacks the lungs, although it can spread to other areas of the body.
The disease is transmitted via airborne droplets of mucus from an actively infected person. TB is highly contagious, but it usually requires prolonged exposure for patients to become infected. In rare cases, a pregnant woman who has active TB may pass the bacteria to her fetus. Patients who are infected are generally not contagious after about two weeks of treatment.
About two to eight weeks after the lungs are infected with the bacteria, the immune system launches an attack. Macrophages (white blood cells that engulf harmful substances that enter the body) form a "wall" around the bacteria, preventing the organism from spreading. If the macrophages are successful, the bacteria can remain dormant in the lungs for years. Patients with this condition will test positive for TB, but they will not express symptoms, and they are not considered contagious.
When the immune system cells are unsuccessful, the white blood cells form granulomas (tumor-like masses of inflamed tissue) in the lungs. The bacteria multiply inside the granulomas, which may enlarge and form nodules. Eventually, the bacteria will break through the granulomatous wall and enter the lungs. Here, the bacteria multiply rapidly, causing an active TB infection. If left untreated, the bacteria can infiltrate other parts of the body, including the kidneys.
Latent TB infection is not contagious and causes no symptoms.
Symptoms of active TB commonly include cough (lasting three or more weeks that may produce discolored or bloody sputum), shortness of breath, pleurisy (inflamed membranes around the lungs), fever, weight loss, night sweats, chills and loss of appetite.
HIV-infected patients who have TB may experience extrapulmonary symptoms (symptoms affecting areas of the body other than the lungs) because the infection can spread to other organs in the body. Symptoms vary depending on the organ(s) affected. For instance, if TB spreads to the spine, back pain may occur, and if the infection has spread to the kidneys, there may be blood in the urine.
General: The standard diagnostic tool for TB is a skin test called the mantoux test (tuberculin test). However, the test cannot determine if the infection is active or inactive. It also cannot tell the difference between a TB infection and a TB vaccination. Therefore, additional tests-such as a chest X-ray, a sputum culture or both, are usually performed to determine whether the patient has an active TB infection.
In May 2005, the U.S. Food and Drug Administration (FDA) approved a blood test that detects the presence of Mycobacterium tuberculosis, although it is not yet widely available. Patients who experienced previous TB infections will test positive for TB in the future, even after they are treated.
Mantoux test (tuberculin test): A mantoux test is the standard diagnostic skin test for TB. During the test, a small amount of purified protein derivative (PPD) tuberculin is injected under the skin of the forearm. After 48 to 72 hours, a qualified healthcare provider will check the arm for a reaction. A positive response is indicated by a hard, raised bump at the injection site.
It is possible to have either false-positive or false-negative test results. A false-positive test usually occurs if the patient is infected with a mycobacterium other than the one that causes TB. A false positive may also occur if the patient has been vaccinated with baccillu Calmette-Guerin (a TB vaccine rarely used in the United States, but commonly used in countries with high infection rates).
QuantiFERON-TB Gold (QFT): The quantiFERON-TB Gold (QFT) test is a type of blood test that detects the presence of the TB bacteria. While this test is FDA approved, and test results take only one day, it is not yet widely available.
Chest X-ray: If a patient has a positive skin test for TB, a chest X-ray may be performed. The X-ray may detect a nodule or cavities in the lungs caused by active TB.
Culture test: If a patient has a positive skin test for TB and the chest X-ray is negative, a culture test may be performed. A qualified healthcare provider may take samples of stomach secretion or sputum. The samples are smeared onto a culture dish and incubated. Within a few hours, the culture is observed for the disease-causing bacteria.
Microscopic-observation drug-susceptibility (MODS): A microscopic-observation drug-susceptibility (MODS) assay may be available in the future to detect TB. In October 2006, researchers reported that the test, which relies on sputum samples, could produce accurate results within seven days. Researchers also claim that the test can identify drug-resistant strains of the TB bacteria. However, this test is currently not available.
General: A combination of antibiotics is typically prescribed for six to 12 months. The exact drugs and length of treatment varies, depending on the patient's age, overall health and state of the disease (latent or active). While the antibiotic rifabutin is used to treat TB in patients who do not have HIV, this drug should not be used to treat HIV patients who are also taking the protease inhibitor saquinavir or the non-nucleoside reverse transcriptase inhibitor delavirdine.
Latent TB: HIV patients who have latent TB have been treated with a daily dose of isoniazid (INH) in order to prevent an infection. Treatment generally lasts about six to nine months. Healthcare physicians monitor patients undergoing treatment closely because side effects may cause life-threatening liver disease. Patients are advised not to take acetaminophen (Tylenol©) and to limit alcohol consumption to decrease the risk of liver damage.
Active TB: Patients diagnosed with active TB typically receive a combination therapy of four antibiotics - isoniazid, rifampin (Rifadin©, Rimactane©), ethambutol (Myambutol©) and pyrazinamide. Some of these drugs may be available in a single combination tablet, which helps make the treatment regimen less complicated. For instance, Rifater© contains isoniazid, rifampin and pyrazinamide. While rifabutin (Mycobutin©) is also used to treat TB in patients who do not have HIV, this drug should not be used to treat HIV patients who are taking the protease inhibitor saquinavir or the non-nucleoside reverse transcriptase inhibitor delavirdine because there is an increased risk of serious side effects like uveitis (inflammation of the inner eye). Treatment generally lasts between six and 12 months.
Astragalus: One clinical trial suggests the potential for benefit of astragalus in patients with TB. Further well-designed clinical trials are required before recommendations can be made.
Beta-sitosterol: Beta-sitosterol and beta-sitosterol glucoside have been studied for the adjunct treatment of tuberculosis with antituberculosis regimens. Only one randomized controlled trial, which included a small number of patients, studied beta-sitosterol and beta-sitosterol for this indication. Larger populations of patients with tuberculosis should be evaluated in randomized controlled trials if conclusions are to be made.
L-carnitine: A preliminary study suggests anti-bacterial activity may be increased in patients with tuberculosis given acetyl-L-carnitine. Well-designed clinical trials are required before recommendations can be made.
Probiotics: As a bacterial reservoir, the nose may harbor many varieties of potentially disease-causing bacteria. There is limited evidence that probiotic supplementation may reduce the presence of harmful bacteria in the upper respiratory tract. More studies are needed to establish this relationship and its implications for health.
Results are mixed regarding the ability of probiotics to reduce infective complications of medical treatment. Reduced incidence of infection has been seen in patients treated for brain injury, abdominal surgery and liver transplantation. Other studies have shown no such reduction in elective abdominal surgery and critical care patients.
HIV-infected patients are encouraged to have a tuberculin test (TB skin test) each year.
Patients who test positive for latent TB, but have no evidence of active TB may consider the baccillu Calmette-Guerin (BCG) vaccine. This vaccine is rarely used in the United States, but it is widely available in areas with high TB infection rates. This is because the vaccine is not very effective in adults. However, it can prevent the infection from spreading outside of the lungs in infants. Patients who receive the vaccine will have false-positive TB skin test results.
Avoid close contact with individuals who are infected with TB.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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- Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com. Copyright © 2007.
- World Health Organization. Frequently Asked Questions about TB and HIV. www.who.int .
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