CLINICAL LAB SCIENEC

388
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
bacteria, called normal flora, that help to ward off invasions of other organisms,
including abnormal bacteria and yeasts. Yeasts reproduce via budding, which can
easily be seen microscopically. Several species of yeasts and fungi are common causes
of infections in humans. The fungal infections most often seen in humans usually
cause minor infections of the hair, nails, mucous membranes, and skin. Candida albicans
often causes systemic infections such as vaginitis and thrush, an oral infection.
Tinea pedis is another example of a fungus; it causes the common infection called
athlete’s foot. The fungal infection ringworm is a type of skin infection. Another
fungal infection of a serious nature when found in the cerebrospinal fluid is that
of Cryptococcus neoformans, which may cause meningitis in infants. People with
chronic diseases may be immunocompromised, and their primary illnesses can be
exacerbated by infections with organisms that are seldom a problem for people who
are healthy. A number of fungal infections may be life-threatening and occur due to
the same reasons that yeasts may become a problem. Persons with AIDS or taking
immunosuppressive drug therapy are at the greatest risk for contracting fungal infections
that may result in death.
Safety in the Microbiology Laboratory
It is inherent to the nature of the work in this department that the worker will
come in close proximity to a variety of microorganisms. Care should be exercised
to avoid becoming a victim by contaminating oneself while handling specimens.
For certain virulent organisms, most of the work will be done under a
safety hood, where small organisms are filtered from the air by a laminar flow
system. Fungal specimens and TB specimens should be tested by using a biological
safety cabinet (Figure 15-1). Procedures should be written to include the use
of safety equipment and supplies in handling certain specimens. An instrument
called a bacterial incinerator (Figure 15-2) is used to routinely remove bacteria
from an inoculating needle or loop, where intense heat renders the organisms
harmless. The student will be instructed as to the use of this instrument,
particularly how to avoid burns, because even
the exterior of this instrument becomes heated,
and the metal needles and loops that have been
treated by heat will remain hot for a period
of time after removal from the incinerator.
Focusing on exposure control (Table 15-1) and
decontaminating work surfaces periodically
is essential to preventing infection of workers
as well as contamination of samples and
equipment.
FIGURE 15-1 Biological safety cabinet for working with contagious
organisms.
Source: Delmar/Cengage Learning.
Resistant Strains of Bacteria
The overuse or injudicious use of antibiotics
when they are not medically indicated has led
to the development of strains of bacteria that
are resistant to most, if not all, antibiotics.
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