Parasitology: Concentration Techniques

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Questions and Answers

What is the primary purpose of concentration techniques in parasitology?

To aggregate parasites into a small volume of sample and remove debris (correct)

To preserve stool specimens

To eliminate all debris from the sample

To detect large numbers of parasites

What is the specific gravity of the zinc sulfate solution required for the zinc sulfate flotation technique?

1.18-1.20 (correct)

1.10-1.15

1.05-1.10

1.25-1.30

What is the purpose of centrifuging the sample for 10 minutes at 500 x G (1500 RPM) in the concentration technique?

To preserve stool specimens

To aggregate parasites into a small volume

To remove as much debris as possible (correct)

To detect large numbers of parasites

Why do parasites float to the surface in flotation techniques?

Because they are less dense than the solution Signup and view all the answers

What is the purpose of straining the specimen through a filter containing a single-layer thickness of gauze?

To remove large debris from the sample Signup and view all the answers

What is the purpose of decanting the supernatant after centrifugation?

To remove as much debris as possible from the sample Signup and view all the answers

What is the principle of the Formalin Ethyl Acetate Sedimentation technique?

Specific gravity Signup and view all the answers

What is the purpose of resuspending the sediment with 1-2 mL of zinc sulfate solution?

To prepare the sample for the zinc sulfate flotation technique Signup and view all the answers

Why is it important to allow the centrifuge to come to a full stop before proceeding with the zinc sulfate flotation technique?

To prevent mixing of the sample Signup and view all the answers

What is the main advantage of the Formalin Ethyl Acetate Sedimentation technique?

Good recovery of most parasites Signup and view all the answers

What is the purpose of adding ethyl acetate to the sample in the Formalin Ethyl Acetate Sedimentation technique?

To facilitate the separation of parasites from fecal debris Signup and view all the answers

What is the main disadvantage of the Formalin Ethyl Acetate Sedimentation technique?

The preparation contains more fecal debris compared to the flotation technique Signup and view all the answers

What is the purpose of centrifuging the sample at 500 x g for 10 minutes in the Formalin Ethyl Acetate Sedimentation technique?

To concentrate the parasites at the bottom of the tube Signup and view all the answers

What is the primary purpose of concentration techniques in clinical parasitology?

To aggregate parasites present in a sample and remove debris. Signup and view all the answers

What is the minimum volume of fecal suspension required for the Formalin-Ethyl Acetate Sedimentation technique?

5 mL Signup and view all the answers

What is the purpose of decanting the top layers of the supernatant in the Formalin Ethyl Acetate Sedimentation technique?

To remove fecal debris from the sample Signup and view all the answers

What is the purpose of adding 10% formalin to the sediment in the Formalin-Ethyl Acetate Sedimentation technique?

To preserve the parasites for further analysis. Signup and view all the answers

What is the purpose of adding 10% formalin to the concentrated specimen in the Formalin Ethyl Acetate Sedimentation technique?

To preserve the parasites for further analysis Signup and view all the answers

Why is distilled water not recommended for use in the Formalin-Ethyl Acetate Sedimentation technique?

It may cause the parasites to be deformed or destroyed. Signup and view all the answers

What is the purpose of using a cotton-tipped applicator to remove debris from the sides of the centrifuge tube in the Formalin Ethyl Acetate Sedimentation technique?

To remove fecal debris from the sample Signup and view all the answers

What is the purpose of centrifuging the sample at 500 x g for 10 minutes in the Formalin-Ethyl Acetate Sedimentation technique?

To concentrate the parasites in the sediment. Signup and view all the answers

What is the function of the cheesecloth-type gauze in the Formalin-Ethyl Acetate Sedimentation technique?

To remove debris from the sample. Signup and view all the answers

What is the purpose of adding ethyl acetate to the sediment in the Formalin-Ethyl Acetate Sedimentation technique?

To facilitate the sedimentation process. Signup and view all the answers

What type of parasites may be recovered using concentration techniques?

Protozoan cysts and other parasitic organisms. Signup and view all the answers

What is the primary purpose of adding zinc sulfate to the specimen?

To make parasites float to the surface for easier identification Signup and view all the answers

What is a disadvantage of using zinc sulfate in concentration techniques?

It collapses the walls of eggs and cysts Signup and view all the answers

What type of parasites are more likely to be missed when using zinc sulfate concentration techniques?

Dense helminth eggs Signup and view all the answers

What is the purpose of removing the top film from the tube using a Pasteur pipette or a bent wire loop?

To place the film on a slide for microscopic examination Signup and view all the answers

What is an advantage of using zinc sulfate concentration techniques?

It yields a cleaner preparation, making it easier for microscopic examination Signup and view all the answers

What type of organisms can be recovered using concentration techniques?

Protozoan cysts, oocysts, and helminth eggs and larvae Signup and view all the answers

Study Notes

Concentration Techniques

Concentration techniques help detect small numbers of parasites that might not be detected using direct wet preparation.
The purpose of concentration is to aggregate parasites into a small volume of sample and remove debris that might hinder parasite visibility.

Formalin-Ethyl Acetate Sedimentation

Principle: Specific gravity, where parasites are heavier than the solution and settle in the sediment, while fecal debris is lighter and rises to the upper layers of the tube.
Procedure:
- Mix specimen well.
- Strain 5mL of fecal suspension through wetted cheesecloth-type gauze into a 15 mL conical centrifuge tube.
- Add 0.85% saline or 10% formalin to bring the volume to 15 mL.
- Centrifuge at 500 x g for 10 minutes.
- Decant supernatant, add 10 mL of 10% formalin, and mix thoroughly with wooden applicator sticks.
- Add 4 mL of ethyl acetate, stopper the tube, and shake vigorously.
- Centrifuge at 500 x g for 10 minutes.
- Decant top layers of supernatant and use cotton-tipped applicator to remove debris from sides of the tube.
- Add several drops of 10% formalin to resuspend concentrated specimen.

Advantages and Disadvantages of Formalin-Ethyl Acetate Sedimentation

Advantages:
- Good recovery of most parasites.
- Easy to perform.
Disadvantages:
- Preparation contains more fecal debris compared to flotation technique.

Zinc Sulfate Flotation Technique

Principle: Flotation techniques, where parasites are less dense than the solutions used and float to the surface during centrifugation.
Procedure:
- Strain specimen through a filter containing a single-layer thickness of gauze into a conical tube.
- Fill the tube with saline or 10% formalin and centrifuge for 10 minutes at 500 x g (1500 RPM).
- Decant supernatant and repeat if necessary.
- Resuspend sediment with 1-2 mL of zinc sulfate solution and fill the tube with additional zinc sulfate to within 2-3 mm of the rim.
- Centrifuge for 2 minutes at 500 x g (1500 RPM).
- Remove one or two drops of the top film using a Pasteur pipette or bent wire loop and place on a slide.
- Add a cover slip and examine microscopically. Iodine can also be added.

Advantages and Disadvantages of Zinc Sulfate Flotation Technique

Advantages:
- More fecal debris is removed, yielding cleaner preparations and making microscopic examination easier.
Disadvantages:
- Some helminth eggs are very dense and will not float, thus, some parasites will be missed.
- Walls of eggs and cysts will often collapse, hindering identification.

Organisms Recovered Using Concentration Techniques

Protozoan cyst
Oocyst
Helminth eggs and larvae

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Description

This quiz covers the methods and materials used in concentration techniques to detect parasites in stool samples, including the use of zinc sulfate solution and iodine solution.