CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
The Development of Microbiology
Around 1676, Anton von Leeuwenhoek happened to discover that magnification
with the use of a series of lenses produced a view of heretofore unknown teeming
colonies of creatures. He described them as vast populations of minute creatures,
as he possibly saw some of them moving and assumed they were indeed alive.
Von Leeuwenhoek and others of the time apparently attached little significance
to this discovery and did not realize the significant impact these images would
have on the lives of everyone living. As early as the 1870s, Joseph Lister and others
discovered that Petri dishes grew a species of bread mold called Penicillium
sp. But it was not until 1945 that Alexander Fleming was awarded the Nobel
Prize in Medicine for the discovery of penicillin; his original endeavors began in
1928 when he learned that a species of bacteria from the genus Staphylococcus
were inhibited or killed by this mold.
For most of the early history of microbiology, which chiefly concerned
bacteria, organisms were grown on nutrient media after collection from both
environmental and body sites. Although viruses are somewhat more difficult to
cultivate than bacteria, great strides have been made in identifying them. Protozoa
and fungi are more readily seen as microorganisms and in some cases may
be identified microscopically. Most procedures for identifying bacterial strains
were developed as intensive manual work, but eventually automated systems
evolved using the information learned from these manual methods to increase
the efficiency and accuracy of microbiology laboratories.
Diagnostic Methodology
In recent years, there has been much development in systems for performing rapid
microbiology. New technologies must be approved by government agencies as to
their accuracy and validity, so the development of new systems is somewhat cumbersome.
Many of the methodologies are extremely expensive, and usually only
the larger laboratories are able to justify the cost of the equipment. Therefore,
some laboratories do little beyond presumptive identifications of bacteria, then
send the specimens to a reference laboratory for further definition. The original
method of culturing a specimen and isolating certain colonies from mixed growth
may still be required even with some of the new technology. Stains are performed
on organisms to determine some of the morphology of the organisms, and these
slides are studied microscopically to gain a hint as to the species of organism that
has been cultured.
A number of time-consuming manual tests, such as tube and slide tests for
certain characteristics of a suspect organism, have now been adapted for quick and
efficient processing in automated systems. Originally, samples were inoculated onto
Petri dishes with differing nutrient qualities and growth characteristics depending
on the constituents of the growth media. These organisms were then stained with a
type of stain called Gram stain, which is actually a series of three stains and a decolorizer.
Some organisms stain as Gram negative or a pink color, while others stain
as Gram positive, a purple color. Further manual tests are performed to place the
organisms onto a flow chart leading toward identification. Fermentation of various
sugars and determinations of metabolic end points from the growing organisms
further lead to a definitive identification.
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