Facts on File Encyclopedia of Health and Medicine

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 character-
istic of mycobacteria is their ability to rapidly
develop resistance to ANTIBIOTIC MEDICATIONS.
Untreated tuberculosis is debilitating and pro-
gressive, giving the appearance that it consumes
the body. This characteristic accounts for the
archaic common name of the disease, “consump-
tion.” 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 likeli-
hood for causing HEARING LOSS (OTOTOXICITY) and
because many strains of M. tuberculosishave devel-
oped 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 MACROPHAGEconsum-
ing 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 granu-
loma. When enough granulomas accumulate,
they interfere with the normal function of the
organ—typically the lungs, though also the kid-
neys, bones, and BRAINwhen M. tuberculosisbacte-
ria migrate to those structures.

Symptoms and Diagnostic Path

Many people who have tuberculosis do not have
symptoms and do not know they have the infec-
tion. Chest X-RAYfor 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 COUGHthat 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, tuber-

culin skin test, and cultures of sputum samples.

When the findings of these diagnostic procedures

are inconclusive, the doctor may conduct addi-

tional tests, including BRONCHOSCOPYor COMPUTED

TOMOGRAPHY(CT) SCAN.

Treatment Options and Outlook

Current treatment regimens use multiple medica-

tions in a rotating pattern over 9 to 12 months.

The first phase of treatment—the initial phase,

which lasts two months—generally involves tak-

ing four medications. The second phase of treat-

ment—the continuation phase, which lasts four to

seven months—generally incorporates a combina-

tion of two medications. The specific drugs depend

on numerous clinical factors, including the per-

son’s HIV status and the sensitivities of the

causative strain of M. tuberculosisfrom sputum cul-

tures.

MEDICATIONS TO TREAT TUBERCULOSIS

Standard Infection

ethambutol isoniazid

pyrazinamid rifabutin

rifampin rifapentine

Resistant Infection

amikacin capreomycin

cycloserine ethionamide

gatifloxacin kanamycin

levofloxacin moxifloxacin

p-aminosalicylic acid protionamide

pyrazinamide 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.

tuberculosis 359