CLINICAL LAB SCIENEC

CHAPTER 6: INTRODUCTION TO INFECTION CONTROL 141
hoarseness may be prevalent. The disease is
found worldwide but most often occurs in
crowded areas of cities and in facilities where
persons are housed in close proximity to each
other. The disease most commonly infects the
respiratory system but may become systemic
in the blood and is capable of affecting any
of the organs of the body . For example, the
disease may also affect the gastrointestinal
and genitourinary systems, as well as the
bones, joints, nervous system, lymph nodes,
and skin.
The main reservoir for TB is humans.
Next in importance, in some instances, are
cows, through their milk, and sometimes
birds who live in close proximity to humans.
A number of similar organisms thought to be
FIGURE 6-9 Administering of PPD skin test.
Source: Delmar/Cengage Learning.
harmless have recently been implicated in cases of pulmonary fibrosis mimicking
TB that have produced lesions . Cleanliness and sanitation of public facilities,
inspection of cattle by government agencies, and control of birds roosting and
nesting in buildings may help alleviate some of the conditions that give rise to
larger and more prevalent reservoirs for the organisms. Secluding those suffering
from TB while symptoms are acute and treatment is ongoing is the most effective
process for avoiding the spread of the organism.
Transmission of the disease is primarily through airborne droplets from sputum
of persons with infectious TB (Figure 6-10). Repeated and close exposure to
an infectious case often leads to the infection of close contacts, including family
members. When a family member is diagnosed with TB, other family members
should be tested and given prophylactic treatment if necessary. Often a person is
infected but lives among the general population for a considerable period of time
before signs and symptoms become noticeable. The organism may incubate for a
period ranging from 4 to 12 weeks before the victim is alerted by symptoms to
seek medical treatment; by then, a number of persons who have come in close
contact with the infected individual may be at risk for contracting the disease.
A person who is infected by the TB bacterium may transmit the disease for as
long as he or she is harboring the organism. This may occur when an asymptomatic
patient is hospitalized for another ailment and TB is then diagnosed. As a general
rule, the person is considered to be able to communicate the disease to others
as long as the bacterium can be isolated from the person’s sputum . Improvement
of sanitary conditions and wearing of PPE are the best methods for preventing
and controlling the spread of TB. Those who have come in close contact with a
person who later develops symptoms of the disease require surveillance, diagnosis,
and possibly early treatment.
Good work practices such as effective hand washing, provision of filtered
ventilation if available, and good housekeeping practices should be maintained
as provided for in the infection control manual . Organisms found in sputum
may survive for days on inanimate objects , necessitating the practice of good
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