TUBERCULOSIS
Tuberculosis is chronic or acute
infectious disease caused by the bacillus
Mycobacterium tuberculosis, which
may affect any tissue of the body but is usually found in the lungs. The name
“tuberculosis” (TB) is derived from the formation by the body of characteristic
cellular structures called tubercles in which the bacilli are trapped and
walled off. The disease rarely occurs in animals in their natural habitat but
is usually found in domesticated cattle, swine and fowl.
Cause of TB
Tubercle bacilli are transmitted
through sputum, 
mainly in airborne droplets or by
dust particles of dried sputum. It is rarely spread by excreta or food
products. Unlike other infectious diseases, tuberculosis has no specific
incubation period. A single 
attack does not confer lasting
immunity; rather, the bacilli may remain latent in the body for a long period,
until a weakening of the body's resistance affords them the opportunity to
multiply and produce symptoms of the disease. Although more than a quarter of the
population harbors tubercle bacilli, the disease becomes evident in only a
relatively small percentage of people. It is most prevalent in areas of
overcrowding and poverty. In some countries in
Detection and Diagnosis
The standard chest X-ray provides a
method of mass screening of people for evidence of early pulmonary
tuberculosis. Although an X-ray will reveal the presence of a lung lesion,
confirmation of its nature requires further testing. The tuberculin test
consists of scratching the skin with a protein substance derived from cultures
of tubercle bacilli. A positive skin reaction indicates the presence of
tuberculosis, whether active or inactive. Diagnosis of active disease is made
by the detection of tubercle bacilli in the sputum.
Early stages of the disease often
produce no symptoms. Symptoms common to all forms of tuberculosis in advanced
stages include fever, fatigue, night sweats, loss of appetite, and loss of
weight. In pulmonary tuberculosis these symptoms are accompanied by respiratory
disturbances such as coughing, chest pains, and production of blood-stained
sputum.
Historical Background
In the early 19th century
the work of the French doctors Gaspard Laurent Bayle and René Laënnec established the forms and stages of
tuberculosis as a disease entity; both Bayle and
Laënnec died of the disease. In 1874 the American doctor Edward Livingston
Trudeau, who was also afflicted with tuberculosis, established 
the Trudeau Laboratory in
The first specific drug for
tuberculosis became available when in 1944 the American microbiologist Selman Abraham Waksman discovered
streptomycin. This discovery was followed by the development in 1948 of PAS (para-aminosalicylic acid) and later by isoniazid
and other antibiotics that revolutionized the treatment of tuberculosis.
Treatment
Hospitalization is often required
during early stages of treatment, but once the disease has been brought under control
the patient may return to normal activity; complete treatment usually takes
from six months to two years. Antibiotics such as rifampicin,
rifabutin, isoniazid, and pyrazinamide are effective against TB when given in varying
combinations. Capreomycin is a powerful drug used
where resistance to others is evident.
Re-emergence of TB
While TB has long been a major
problem in developing countries, it was widely thought to have been eliminated
in the developed world as a result of improved social conditions, mass
screening, and the effective use of antibiotics and the BCG vaccine. However,
in the 1980s it re-emerged in the West, for example in
According to the World Health
Organization, the worldwide increase in TB is such that in 1996 more people
were infected with the disease than at any other time. Rising poverty and homelessness,
increased migration and inadequate or reduced public health services are all
factors. In developed countries many research facilities have been closed and
screening programs for disadvantaged groups such as the homeless are no longer
readily available as was the case in previous decades.
Robert koch 1843 – 1910
German scientist and Nobel laureate,
who founded modern medical bacteriology, isolated several disease-causing bacteria,
including those of tuberculosis, and discovered the animal vectors of a number
of major diseases.
After a brief tenure at the
Koch's first major breakthrough in
bacteriology occurred in the 1870’s, when he demonstrated that the infectious
disease anthrax developed in mice only 
when the disease-bearing material
injected into a mouse's bloodstream contained viable rods or spores of Bacillus
anthracis. Koch's isolation of the anthrax bacillus was of momentous import,
because this was the first time that the causative agent of an infectious
disease had been demonstrated beyond a reasonable doubt. It now became clear
that infectious diseases were not caused by mysterious substances but instead
by specific micro-organisms—in this case, bacteria. Koch also showed how the
investigator must work with such micro-organisms, how to obtain them from
infected animals, how to cultivate them artificially, and how to destroy them.
He revealed these observations to the great German pathologist Julius Friedrich
Cohnheim and his associates, one of whom was the
bacteriologist Paul Ehrlich, the founder of modern immunology.
In 1880 after completing important
work on the bacteriology of wound infections Koch was appointed government
adviser with the Imperial Department of Health in 
dreaded disease. Koch's findings
were confirmed by investigators around the world. The discovery led to an
improvement in diagnosis by means of finding evidence of the bacilli in bodily
excretions, especially sputum.
Koch now focused his attention on cholera,
which had reached epidemic levels in
In 1891 Koch became director of the
Institute for Infectious Disorders in
