Tuberculosis (cont.)
Is there a vaccine against tuberculosis?
Bacille Calmette Guérin, also known as BCG, is a vaccine given throughout many parts of the world. It is derived from an atypical mycobacterium but offers some protection from developing active tuberculosis, especially in infants and children. This vaccination is believed to be important in parts of the world where TB is quite common. This is not the case in the United States. When BCG has been administered, future PPD and Tine skin tests remain positive and can cause some confusion when trying to diagnose TB. It is also important to realize that even with a BCG vaccine in childhood, tuberculosis can still occur in an adult exposed to the tuberculosis bacteria, which calls into question the real utility and effectiveness of this vaccination.
How is tuberculosis treated?
A person with a positive skin test, a normal chest x-ray, and no symptoms
most likely has only a few TB germs in an inactive state and is not contagious.
Nevertheless, treatment with an antibiotic may be recommended for this person to
prevent the TB from turning into an active infection. The antibiotic used for
this purpose is called isoniazid (INH). If taken for six to 12 months, it will
prevent the TB from becoming active in the future. In fact, if a person with a
positive skin test does not take INH, there is a 5%-10% lifelong risk that the
TB will become active.
Taking isoniazid can be inadvisable (contraindicated) during pregnancy or for
those suffering from alcoholism or liver disease. Also, isoniazid can have side
effects. The side effects occur infrequently, but a rash can develop, and the
patient can feel tired or irritable. Liver damage from isoniazid is a rare
occurrence and typically reverses once the drug is stopped. Very rarely,
however, especially in older people, the liver damage (INH hepatitis) can even
be fatal. It is important therefore, for the doctor to monitor a patient's liver
by periodically ordering blood tests called "liver function tests" during the
course of INH therapy. Another side effect of INH is a decreased sensation in the extremities referred to as a peripheral neuropathy. This can be avoided by taking vitamin B6 (pyridoxine), and this is often prescribed along with INH.
A person with a positive skin test along with an abnormal chest x-ray and
sputum evidencing TB bacteria has active TB and is contagious. As already
mentioned, active TB usually is accompanied by symptoms, such as a cough, fever,
weight loss, and fatigue.
Active TB is treated with a combination of medications along with isoniazid.
Rifampin (Rifadin), ethambutol (Myambutol), and pyrazinamide are the drugs
commonly used to treat active TB in conjunction with isoniazid (INH). Four drugs
are often taken for the first two months of therapy to help kill any potentially
resistant strains of bacteria. Then the number is usually reduced to two drugs
for the remainder of the treatment based on drug sensitivity testing that is
usually available by this time in the course. Streptomycin, a drug that is given
by injection, may be used as well, particularly when the disease is extensive
and/or the patients do not take their oral medications reliably (termed "poor
compliance"). Treatment usually lasts for many months and sometimes for years.
Successful treatment of TB is dependent largely on the compliance of the
patient. Indeed, the failure of a patient to take the medications is the most
important cause of failure to cure the TB infection. In some locations, the
health department demands direct monitoring of patient compliance with therapy.
Surgery on the lungs may be indicated to help cure TB when medication has failed, but in this day and age, surgery for TB is unusual. Treatment with appropriate antibiotics will usually cure the TB. Without treatment, however, tuberculosis can be a lethal infection. Therefore, early diagnosis is important. Those individuals who have been exposed to a person with TB, or suspect that they have been, should be examined by a doctor for signs of TB and screened with a TB skin test.
Next: What is drug-resistant TB? »
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