CLINICAL LAB SCIENEC

390
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
This may occur based on technology, such as that which identifies bacteria using
gene probes and fluorescent labeling, that takes less time than traditional methods
and is extremely accurate.
Many advances in technology addressing the need for quicker and more
accurate identification of microorganisms such as bacteria and viruses have
occurred over the past few decades. This technology provides sensitivity panels
for prescribing correct antibiotics in a matter of hours rather than days. Traditional
methods used since the beginnings of microbiology involve culturing
the organism(s) on Petri dishes containing nutritive media and, after growth
of visible colonies is accomplished, using biochemical reagents to determine
characteristics specific to a particular organism. There are instruments that still
use these traditional methods to identify organisms, but another method uses
identification of the products of metabolism peculiar to each strain of bacteria.
Some of the instruments used frequently in the clinical laboratory are as
follows:
Manufacturer
Becton Dickinson
Biomerieux
Dade Behring (Siemens)
Instrument Name
Phoenix
ViTek
MicroScan
An evolving tool uses gene probes to identify genes found in bacteria and
viruses. This involves taking a short snippet or fragment of DNA or RNA from
a single stranded segment of the double helix arrangement of an entire gene as
it naturally occurs. The double helical structure is “unwound” to single strands
by chemical means before testing occurs. Because of its specificity toward a particular
genetic sequence, this segment can hunt for its complementary strand or
fragment amid all of the cellular components that may be encountered in the
specimen, which may also contain cellular materials and proteins as well as the
infecting organism. The fragment being searched for in the patient specimen is
basically a mirror image of the gene probe that is chasing the elusive goal of its
identical mate. The fragment will pair with a complementary genetic sequence
that has been marked by a chemical or radioactive substance that will bind to
a given gene. This marked genetic sequence is then used as a tag to identify
or isolate the gene from the microorganism that pairs with the marked genetic
structure.
Another technique showing great promise is that of fluorescent labeling.
This process is independent of the need to grow the microorganisms. This technique
can be used to rapidly detect all viable cells. Including both damaged and
fastidious microorganisms that might be difficult to grow in a culture. In addition,
there is no need for large numbers of organisms so there is no need for an
incubation period.
Technical and financial benefits gained from implementation of some of these
methods are significant but they are in reality only useful for those laboratories
with a large number of determinations needed on a regular basis. No doubt
technology will move in the direction of even more definitive testing, including
systems engineered for smaller laboratories and even bedside testing.
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