CLINICAL LAB SCIENEC

140
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
airborne pathogens requiring specific training as protection against the organism.
Mycobacterium tuberculosis is the organism that causes TB. (As a point of
interest, certain parts of the world have colonies of persons infected with a similar
organism that causes the disease of leprosy. That organism is called Mycobacterium
leprae , and it has been infecting persons at least since biblical times.) TB
was thought to have become almost completely eradicated in the developed and
modern world, but in the past few years, large pockets of the disease have broken
out, dispelling the belief that there was no longer a danger from this disease.
Drug-resistant cases are being discovered almost daily, and cases of atypical TB
are on the rise. Atypical TB may include diseases similar to TB but fostered by a
different causative organism than M. tuberculosis.
Before the development of antibiotics effective against the TB organism,
treatment consisted of isolation in a sanitarium. The focus of treatment was to
help the patient become as healthy as possible through adequate nutrition and
the provision of fresh air . Patients stayed until their sputum no longer carried
the organism. This sometimes occurred when areas of the lungs became calcified
and effectively walled off colonies of the TB organism. Isolation or quarantining
was the only treatment available and often patients were kept in sanitariums for
years before they were released to live among the uninfected population. When
relapses occurred, as they almost invariably did, patients were readmitted to a
sanitarium.
TB is caused by a bacillus (rod-shaped bacterium) that is more difficult to
treat than many bacterial organisms. Different strains to which humans are also
susceptible occur in both birds and cattle. The diagnosis is made by performing
a skin test to determine if the patient has developed a reaction against this
particular organism. If the skin test is positive, a chest radiograph is obtained to
determine if the person is in an active stage of the disease.
Routine tuberculin skin tests to determine if an unknown exposure has
occurred are required before entering a clinical facility for both students and
medical workers. This is routinely done as part of the physical examination on
health care students and new employees in medical facilities. OSHA regulations
require testing twice per year to determine if a medical worker or student has been
exposed to the M. tuberculosis organism. Medical facilities will not allow anyone
to work in direct contact with patients unless the worker has been tested for the
disease or for recent exposure. Both actual infection and recent exposure will yield
positive results on the PPD (tuberculin) skin test (Figure 6-9). The PPD skin test is
an intradermal injection that will cause a positive reaction for those who have ever
been exposed to the TB organism.
Although antibiotics are effective except in the more resistant strains of
M. tuberculosis , the administration of antibiotics for treating uncomplicated
cases of TB requires daily doses of the antibiotics isoniazid and rifampin for
2 months, followed by 4 months of additional self-administration of these antibiotics.
There is an 80% mortality rate for those with the multidrug–resistant
strains of the organism.
Symptoms and signs of the disease include fatigue , fever , and weight loss.
These signs and symptoms may occur early in the illness. During the advanced
states of the disease, cough, chest pain, hemoptysis (spitting up of blood ), and
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