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Introduction
Pulmonary tuberculosis (TB) is a contagious bacterial
infection caused by Mycobacterium tuberculosis (M.
tuberculosis). The lungs are primarily involved,
but the infection can spread to other organs.
Causes
Tuberculosis is caused
by Mycobacterium
Tuberculosis, an organism found throughout the
world.
Respiratory droplets most often
spread it person-to-person when people cough.
Initially, the infection is
acquired from another person. Once the organism
enters the body, it spreads via the bloodstream and
lymph system throughout the body. This is called
primary
Tuberculosis, and often
there are no symptoms. The immune system fights off
the infection, destroying the majority of
organisms. Some become dormant and survive within
the body for years or even decades. These organisms
usually do not cause any problems.
However, in a few cases,
reactivation of the disease occurs. This does not
require any new infection. The organism, dormant
and inactive for years, has become active again.
The risk of reactivation
increases if the immune system is weakened for any
reason.
On average, a normal person who
has been infected with
Tuberculosis has about a
10% chance of developing a reactivation of the
disease over the course of their lifetime. In people
with HIV, however, they have a risk of about 7% per
year.
In the past, it was thought that
almost all adult cases of
Tuberculosis were due to
reactivation. However, newer testing methods have
revealed that a sizeable number of adult cases may
actually be due to newly acquired infections,
especially in areas where there are a large number
of people with
Tuberculosis.
People from certain parts of the
world, such as the Philippines, China, Southeast
Asia, Haiti, and India have a much higher risk of
having resistant
Tuberculosis. Resistant
Tuberculosis
occurs when the organism is not sensitive to the
usual anti-Tuberculosis
medicines.
Symptoms
Additional
symptoms that may be associated with this disease:
Screening and Diagnostics
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Chest x-ray
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Sputum cultures
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Tuberculin skin test
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Bronchoscopy
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Thoracentesis
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Chest CT
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Interferon (IFN)-gamma blood
test. This type of test looks for an immune response
to proteins produced by M. tuberculosis. In December
2004, the FDA approved the QuantiFERON-TB Gold (QFT-Gold)
test as an alternate to the traditional tuberculin
skin test (TST).
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Rarely, biopsy of the affected
tissue (typically lungs, pleura, or lymph nodes)
Treatment
Tuberculosis should be
started on all individuals in whom the doctor
suspects the disease. If there is any risk that the
patient may not take the medications, or may expose
others, then initial treatment needs to be done in
the hospital. Most of the time, other household
members have already been exposed, and isolation
from them is not needed. However, if there is a
possibility of new exposures, then isolation is in
order. In the hospital, patients are placed in a
special room (called a negative pressure room), to
prevent spread of the disease to staff and others.
All hospital staff and family members in contact
with the patient will have to wear protective masks.
Treatment -- there are many
options and treatment needs to be tailored to the
individual and his lifestyle, as well as to the
location and type of the infection
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There are two main conditions
of treatment. In the first case, the patient is
treated at home, coming in for periodic check-ups.
In the second, called DOT (directly observed
therapy), the patient comes into the health
department or other agency 2-3 times a week for
medication, to ensure that he is actually taking
his medicines.
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The four main drugs used to
treat
Tuberculosis are
Isoniazid,
Rifampin,
Pyrazinamide, and either Ethambutol or
Streptomycin. Usually four (4) of these drugs are
given in combination to treat almost all
Tuberculosis
infections.
Treatment is with four
medications until the tests identify which anti- Tuberculosis
medicines will be most effective. Medications are
adjusted accordingly. Usually, all four are
continued for about 4-6 weeks. If the organism
proves to be sensitive to
Isoniazid and Rifampin,
they are continued, and Ethambutol or Streptomycin
is stopped.
Pyrazinamide is continued for 8 weeks then
stopped. Therapy is continued for at least 6
months, or for at least 3 months after the
cultures are negative -- whichever is longer.
There are various combinations
of treatment and the best option will have to be
tailored to the patient's needs by the doctor and
the health care department.
In patients with HIV, they need
to continue treatment for a minimum of 9 months,
or for 6 months after the cultures are negative.
If cultures are not available
to guide the doctor, options will need to be
discussed with a specialist because the type,
length, and method of treatment all vary.
Directly observed therapy (DOT)
is more expensive to administer, but it ensures
that the patient takes his medicines, especially
in those with drug-resistant
Tuberculosis, and in
those who refuse to take their medication or have
difficulty following directions.
Treatment for
Tuberculosis outside
the lungs is usually the same as pulmonary
Tuberculosis, but it
is usually continued for at least 9 months.
Steroids can be used for people
with
Tuberculosis
Meningitis and
Tuberculosis
Pericarditis to help
reduce inflammation.
Streptomycin should not be used
by pregnant women.
Pyrazinamide use
during pregnancy is not advised either.
All treatment starts with
multiple medications because of the risk of
resistance if only 1 or 2 medications are used.
Treatment should start with all four, and then
altered according to results.
Patients should take all of
their medicines until the doctor tells then to
stop. If the doctor's orders are not followed,
there is a high risk of not adequately treating
the infection. The organism may become resistant,
making repeat infection difficult to treat.
lymphadenitis is treated with surgery to remove all
infected lymph nodes, after which the patient is
placed on anti-TB medications.
Tuberculosis
Meningitis --
using the four anti-TB medications described above,
treatment has to be started even before all of the
test results are back. Occasionally, steroids may
also be used in the case of nerve deficits.
Tuberculosis
Pericarditis -- requires drainage of the fluid and
anti-TB medications. In some cases, the sac
surrounding the heart may have to be removed.
Tuberculosis
peritonitis -- is treated with the usual combination
of anti-TB medications.
Tuberculosis
salpingitis -- this is treated with the usual
anti-TB medications. If there is a large mass, or if
the TB does not respond to medication, surgery may
be necessary.
The risk of contracting
drug-resistant TB increases in regions known to have
a high incidence of drug-resistant TB. Other high
risk factors for drug resistant TB include close
contact with someone with drug-resistant TB,
previous unsuccessful treatment for TB, and previous
failure to take all medicines and complete
treatment. The risk of drug-resistant TB is
especially high in the United State in large urban
centers, such as New York, Dallas, and Los Angeles.
In those with drug-resistant TB, the infection is
almost always fatal, unless an alternative drug
regimen is found and followed. This requires the
input of trained specialists to help structure
treatment options.
Complications
Pulmonary TB can cause permanent lung damage if not
treated early.
All medications used to treat TB have some toxicity.
Rifampin and isoniazid may both cause a non-infectious
hepatitis. Rifampin may also cause an orange or brown
coloration of tears and urine.
Those taking ethambutol should have their vision
monitored, as this drug sometimes affects the eye. Any
rash, abdominal pain, jaundice, or tingling in toes or
fingers may be a sign of drug toxicity and should be
reported to your doctor immediately.
Other complications include drug resistance to
particular TB strains and a relapse of the disease in
some patients.
Prevention
TB is a preventable disease, even in those who have
been exposed to an infected person. Skin testing (PPD)
for TB is used in high risk populations or in
individuals who may have been exposed to TB, such as
health care workers.
A positive skin test indicates prior TB exposure.
Preventive therapy should be discussed with your
doctor. Individuals exposed to tuberculosis should be
skin tested immediately and a follow-up test should be
done at a later date, if the initial test is negative.
Prompt treatment is extremely important in controlling
the spread of tuberculosis for those who have already
progressed to active TB disease.
A BCG vaccination to prevent TB is given in some
countries with a high incidence of TB, but its
effectiveness remains controversial. It is not
routinely used in the United States. People who have
had BCG may still be skin tested for TB and results of
testing (if positive) discussed with one's doctor.
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