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.
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Symptoms of Tuberculosis
Only about 10 percent of those infected with TB develop the disease. The first
symptoms of an active case of TB may be so commonplace that they are often
dismissed as the effects of a cold or flu. The individual may get tired easily,
feel slightly feverish or cough frequently. It usually goes away by itself, but
about in about half the cases, it will return. For people who have the
disease, TB can cause lung or pleural (the lining of the lung) disease or it
may spread through the body via the blood. Often people do not seek the advice
of a doctor until they have pronounced symptoms, such as pleurisy (a sharp
pain in the chest when breathing deeply or coughing) or the spitting up of
blood. Neither of these symptoms is solely of tuberculosis, but
they should not be ignored. Other symptoms include fever, loss of appetite,
weight loss and night sweats.
About 15 percent of
people with the disease develop TB in an organ other than the lung, such as the
lymph nodes, GI tract, and bones and joints.
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Diagnosis of Tuberculosis
If a person has a significant reaction upon being tuberculin skin-tested for the
first time, additional laboratory and x-ray examinations are necessary to
determine if the individual has active TB. Tuberculosis can mimic
other diseases, such as pneumonia, lung abscesses, tumors and fungal infections, or occur along with them. For a proper
diagnosis, therefore, a doctor will rely on symptoms and other physical signs;
a person's history of exposure to TB and x-rays that may show evidence of TB
infection (usually in the form of lesions or cavities in the lungs). TB bacilli
grown in cultures of sputum or other specimens provide a positive diagnosis.
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Treatment of Tuberculosis
With treatment, the chances of full recovery is good. Although several treatment
protocols for active TB are in wide use by specialists, and protocols sometimes
change due to advanced in our understanding of optimal therapy, they generally
share three principles:
- The regimen must include several drugs to which the
organisms are susceptible.
- The patient must take the medication on a regular
basis.
- Therapy must continue for a sufficient time.
Also, treatment recommendations are subject to change depending upon both the characteristics
of the particular organism being treated and newer advances in therapeutic
agents. Thus, consultation on treatment strategies with local public health and
infectious disease experts is always advisable.
Isoniazid (INH) is one of the most common drugs used for TB. Inexpensive, effective and easy to take, it
can prevent most cases of TB and, when used in conjunction with other drugs,
cure most TB. INH preventive treatment is recommended for individuals who have:
- close contact with a person with infectious TB
- positive tuberculin skin test reaction and an
abnormal chest x-ray that suggests inactive TB
- a tuberculin skin test that converted from negative
to positive within the past two
- a positive skin test reaction and a special medical
condition or who are on corticosteroid therapy
- a positive skin test reaction, even with none of the
above risk factors (in those under 35)
Isoniazid and rifampin are the keystones of treatment, but because of increasing resistance to them,
pyrazinamide and either streptomycin sulfate or ethambutol HCL are added to
regimens. If the patient is unable to take pyrazinamide, a nine-month regimen
of isoniazid and rifampin is recommended.
Even if susceptibility
testing reveals that the patient is infected with an isoniazid-resistant
strain, the isoniazid component is continued because some organisms may yet be
sensitive. In addition, two drugs to which the organisms are likely to be
sensitive also are incorporated into the regimen.
The beginning phase of
treatment is crucial for preventing the emergence of drug resistance and
ensuring a good outcome. Six months is the minimum acceptable duration of
treatment for all adults and children with culture-positive TB.
Drug resistance may be
either primary or acquired. Primary resistance occurs in patients who have had
no previous antimycobacterial treatment. Acquired resistance occurs in patients
who have been treated in the past, and it is usually is a result of
non-adherence to the recommended regimen or incorrect prescribing.
It has been estimated
that one in seven cases of tuberculosis is
resistant to drugs that previously cured the disease. Resistance arises when
patients fail to complete their drug therapy, lasting six months or longer. The
hardiest TB bacteria are allowed to survive as a result, and as they multiply,
they spread their genes to a new generation of bacteria - and to new victims.
The drug-resistant forms
of TB that do not respond to the usual drug therapy might be treatable by
other, sometimes more toxic drugs. Officials of the Center for Disease Control
and Prevention call for aggressive intervention to prevent the further spread
of drug-resistant TB, including finding 'every TB patient' and
ensuring that patients complete their drug therapy. To accomplish this,
increasing use of directly observed therapy (DOT) is being used - that is, the
actual, documented observation of the patient when he or she takes the
medicine. This method has been shown to reduce the likelihood of treatment
failures.
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