Encyclopedia of Health and Medicine

tuberculosis 359
tuberculosis An illness resulting from INFECTION
with the MICROBE Mycobacterium tuberculosis.
Though tuberculosis most commonly infects the
LUNGS, the disease may involve other organs as
well, notably the KIDNEYS. Health experts estimate
more than 2 billion people worldwide have active
(symptoms are present) or latent (symptoms are
not present) tuberculosis. An important characteristic
of mycobacteria is their ability to rapidly
develop resistance to ANTIBIOTIC MEDICATIONS.
Untreated tuberculosis is debilitating and progressive,
giving the appearance that it consumes
the body. This characteristic accounts for the
archaic common name of the disease, “consumption.”
Tuberculosis was a leading cause of death
throughout the world until the discovery of the
FUNGUS-derived antibiotic streptomycin in 1944.
Today’s treatment regimens seldom incorporate
streptomycin, however, because of its high likelihood
for causing HEARING LOSS (OTOTOXICITY) and
because many strains of M. tuberculosis have developed
resistance to it.
When breathed into the lungs, M. tuberculosis
BACTERIA infect macrophages, white BLOOD cells
responsible for consuming invading pathogens, in
the alveoli. Rather than the MACROPHAGE consuming
the M. tuberculosis bacterium, however, the
bacterium takes over the macrophage. Other cells
of the IMMUNE RESPONSE surround the infected
macrophage, enclosing it within a GRANULOMA. The
bacteria may remain dormant within the granuloma.
When enough granulomas accumulate,
they interfere with the normal function of the
organ—typically the lungs, though also the kidneys,
bones, and BRAIN when M. tuberculosis bacteria
migrate to those structures.
Symptoms and Diagnostic Path
Many people who have tuberculosis do not have
symptoms and do not know they have the infection.
Chest X-RAY for other diagnostic reasons may
detect lesions in the lungs; other people learn they
have tuberculosis through routine tuberculin SKIN
testing such as many states in the United States
require for people who work with the public, such
as health-care workers and food service workers.
When symptoms are present they include
• prolonged, productive COUGH that may include
blood (HEMOPTYSIS)
• unintended weight loss
• FEVER
• night sweats
• fatigue
• wheezing or feeling of tightness in chest
The diagnostic path includes chest X-ray, tuberculin
skin test, and cultures of sputum samples.
When the findings of these diagnostic procedures
are inconclusive, the doctor may conduct additional
tests, including BRONCHOSCOPY or COMPUTED
TOMOGRAPHY (CT) SCAN.
Treatment Options and Outlook
Current treatment regimens use multiple medications
in a rotating pattern over 9 to 12 months.
The first phase of treatment—the initial phase,
which lasts two months—generally involves taking
four medications. The second phase of treatment—the
continuation phase, which lasts four to
seven months—generally incorporates a combination
of two medications. The specific drugs depend
on numerous clinical factors, including the person’s
HIV status and the sensitivities of the
causative strain of M. tuberculosis from sputum cultures.
Standard Infection
ethambutol
pyrazinamid
rifampin
MEDICATIONS TO TREAT TUBERCULOSIS
Resistant Infection
amikacin
cycloserine
gatifloxacin
levofloxacin
p-aminosalicylic acid
pyrazinamide
isoniazid
rifabutin
rifapentine
capreomycin
ethionamide
kanamycin
moxifloxacin
protionamide
viomycin
Symptoms in most people improve dramatically
within three weeks of starting medication, though
clinical changes (X-ray) often do not become
apparent for several months. Treatment regimens
are complex, and the medications can cause
unpleasant side effects, the combination of which
tempts people to stop taking the medications.