Clinical Parasitology Lab Midterm: Stool Smear Prep & Staining

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary purpose of using permanent stain in stool smear preparation?

To observe detailed features of protozoa by making their extracellular organelles visible

To detect helminth eggs or larvae

To analyze samples using the 40x objective

To provide a permanent record of a patient's specimen for review by consultants (correct)

How many fields must be reviewed before a slide can be considered negative?

400 fields

200 fields

100 fields

300 fields (correct)

What is the sample of choice for permanent staining?

Fresh sample submitted for staining

Thinly prepared slide made of PVA-preserved sample (correct)

Thickly prepared slide made of SAF-preserved sample

Fixed sample using Schaudinn's fixative

What is the limitation of using permanent stain?

It is not useful in detecting helminth eggs or larvae Signup and view all the answers

What is the preferred stain for Schaudinn-preserved samples?

Iron hematoxylin Signup and view all the answers

What is the first step in preparing a smear for staining?

Place the prepared smear in a coplin jar containing Schaudinn's fixative Signup and view all the answers

What is the purpose of using several layers of paper towel in preparing the PVA-preserved stool sample for staining?

To remove excess PVA from the stool sample Signup and view all the answers

What is the advantage of using Trichrome stain (Wheatley modification)?

It uses reagents with a relatively long shelf life and is easy to perform Signup and view all the answers

What should be done to a fresh sample submitted for staining?

Allow it to dry and then fix it Signup and view all the answers

What is the recommended temperature for drying the smear in preparing the PVA-preserved stool sample for staining?

Room temperature Signup and view all the answers

What is the preferred stain for SAF-preserved samples?

Iron hematoxylin Signup and view all the answers

What is the purpose of adding a few drops of permount to the SAF-preserved specimen?

To let it dry Signup and view all the answers

What is the purpose of using an applicator stick in preparing the PVA-preserved stool sample for staining?

To apply the sample to the slide Signup and view all the answers

What is the purpose of using 70% ethanol in preparing the PVA-preserved stool sample for staining?

To remove excess PVA from the sample Signup and view all the answers

What is the recommended method for examining the SAF-preserved specimen under a microscope?

Add one drop of oil immersion to the slide Signup and view all the answers

What is the purpose of letting the smear dry overnight at room temperature or 2-3 hours at 35 degrees Celsius?

To prepare the sample for examination Signup and view all the answers

What is the purpose of centrifuging the sample at 1,500 rpm for 1 minute?

To concentrate the sediment Signup and view all the answers

What is the function of albumin in the staining procedure?

To mix with the sediment Signup and view all the answers

Why are acid-fast stains used for certain bacteria?

Because they have a high lipid content Signup and view all the answers

What is the purpose of using Kinyoun's carbolfuchsin in the acid-fast staining procedure?

To stain the bacteria Signup and view all the answers

Why do bacteria with high lipid content require acid-fast stains?

Because they are resistant to decolorization Signup and view all the answers

What is the purpose of using Malachite green in the acid-fast staining procedure?

To counterstain the specimen Signup and view all the answers

What is the advantage of using acid-fast stains?

They can detect bacteria with high lipid content Signup and view all the answers

How many fields should be examined under the microscope?

200 to 300 fields Signup and view all the answers

Why is it important for laboratory technicians to be knowledgeable about specimen collection?

To explain the procedure to patients, families, or other health care professionals Signup and view all the answers

What is the primary purpose of emphasizing proper hygiene and preventive measures during specimen collection?

To prevent contamination of the laboratory environment Signup and view all the answers

What is the characteristic of mycobacteria?

Resistance to decolorization with acid alcohol Signup and view all the answers

What is the purpose of using 100x oil immersion objective?

To confirm internal morphology Signup and view all the answers

What type of tape should be avoided when collecting a specimen using the cellophane tape method?

Frosted tape Signup and view all the answers

What is the composition of acid alcohol?

10ml Sulfuric Acid + 90ml Absolute Ethanol Signup and view all the answers

What is the recommended way to apply the adhesive side of the tape during specimen collection?

Using a rocking motion Signup and view all the answers

What is the stain used for detection of oocyst of Cryptosporidium, Isospora & Cyclospora?

Modified acid fast stain Signup and view all the answers

What is the purpose of using a low power objective during the microscopic examination?

To reduce the intensity of the light Signup and view all the answers

What is the purpose of cellophane tape preparation?

Detection of Enterobius vermicularis Signup and view all the answers

What is the purpose of using a clean glass microscopic slide during the specimen collection procedure?

To ensure the eggs are not obscured by debris Signup and view all the answers

Why is it important to collect specimen in the morning for cellophane tape preparation?

Because the gravid female worm lays numerous eggs in the perianal region at night Signup and view all the answers

What is the benefit of using a modified acid fast stain?

Detection of oocyst of Cryptosporidium, Isospora & Cyclospora which may be difficult to detect with routine stain Signup and view all the answers

What is the significance of non-acid fast organisms?

They lack cell walls fortified with mycolic acid Signup and view all the answers

Study Notes

Stool Smear Preparation & Permanent Staining

Permanent stain preparation provides a permanent record of a patient's specimen, allowing for review and consultation if difficulties arise in identification.
Permanent stain is designed for analysis using the oil immersion objective (100x), and 300 fields must be reviewed before the slide can be considered negative.
Permanent stain is used to detect protozoan cysts and trophozoites by making their intracellular organelles visible.

Staining Techniques

Two common stains used in routine O&P testing are:
- Trichrome (Wheatley modification)
- Iron hematoxylin
Wheatley trichrome stain is the most widely used permanent stain, preferred by many users due to its relatively long shelf life and ease of performance.
Iron hematoxylin stain reveals excellent morphology of intestinal protozoa, with nuclear details stained clearer and sharper compared to trichrome.

Smear Preparation for Staining

For fresh stool samples, allow the sample to dry and then fix it in Schaudinn's fixative.
For PVA-preserved samples, mix the stool sample with PVA and apply it to a glass slide.
For SAF-preserved samples, mix the specimen well, add a few drops of permount, and let it dry.

Acid Fast Staining

Acid fast stains are used to stain bacteria that have a high lipid (long chain of mycolic acid) and wax content in their cell walls, making them resistant to decolorization with acid alcohol decolorizers.
The acid fast stain takes advantage of the waxy content of the cell walls to maximize detection.
Mycobacteria are the most commonly encountered acid-fast bacteria.
Coccidian oocyst and other acid-fast organisms will appear pink or red, while the background may appear blue or green depending on the counterstain used.

Cellophane Tape Preparation

Cellophane tape preparation is the specimen of choice for the detection of Enterobius vermicularis.
The adult female worm may also be seen in the perianal region.
Specimen collection is critical, and laboratory technicians must be knowledgeable regarding collection procedures.
Emphasize the importance of exercising proper hygiene and preventive measures during specimen collection to avoid spreading infectious eggs into the environment.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the preparation and permanent staining of stool smears in clinical parasitology laboratory, including the use of oil immersion objective and detection of protozoan cysts and trophozoites.