CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
14. Discard all supplies used for the procedure in the appropriate containers. A disinfectant
should be used to clean the work surfaces and equipment should be
cleaned and restored to its former position. Gloves should be discarded appropriately
and the hands washed thoroughly in accordance with established policies.
15. After 24 hours, examine the agar plate for characteristic bacterial growth. Note
that personal safety precautions (wash hands, gloves, clean up) should be followed
before and after examining the plate.
Quality Control
Known specimens are cultured and stained on a regular basis to insure conditions
are adequate to support the culturing of bacteria.
Reporting of Results
Worksheets are generally kept for each culture initiated. If there is no growth, the plate
is reported as “no growth” and is incubated for an additional day. When colony growth is
observed, it is important to perform a colony count for some organisms. Samples of colony
growth are subcultured (transferred to other agar plates) and the organisms identified
and records. More than one organism may be present.. The final report most often takes
two days, and should include identification of all organism(s) and if appropriate, an antibiotic
sensitivity report indicating the antibiotic to which the organism(s) is/are sensitive.
MANUAL MICROBIOLOGY PROCEDURE #2
Preparation of Smears
Principles
In some cases, exudates (discharge as from a wound) or body fluids such as cerebrospinal
fluid (CSF) can be stained directly to gain critical information regarding the
type of bacteria that may be present. This is often attempted in cases where a quick
presumptive identification is crucial for the patient’s health, such as with organisms in
CSF. Most slides for staining, however, are obtained from cultures. If mixed cultures of
more than one type of bacteria (as observed on an agar plate) are present, separate
testing must be done on each type of bacteria. Note that it is not possible to separate
the various species of organisms in broth or other liquid mixed cultures. Bacterial
smears for staining must be heat fixed prior to initiating the staining process to prevent
the organisms from washing off the slide during the staining procedure.
Several methods are employed for preparing smears for staining. The method
selected depends upon the type of specimen and type of media, as well as personal
preference of the laboratory professional or the skill level of the worker.
Equipment and Supplies
1. Gloves, disposable paper towels, and disinfectant or other cleaning solution
2. Swabs tipped with cotton or synthetic material (to be used to transfer organisms)
or reusable or sterile disposable inoculating metal loops and needles.
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