Parasitology and Sample Collection Guide

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of a parasite in its life cycle?

To cause death to its host quickly.

To reproduce outside of a host.

To depend on another living creature for food and habitat. (correct)

To live independently from other organisms.

Which of the following is NOT a stage of parasite infection?

Sporophyte (correct)

Cyst

Larva

Ovum

What type of sample is NOT listed as suitable for detecting parasites?

Sputum

Blood

Urine

Hair (correct)

What is the acceptable amount of stool required for a parasite test?

2 to 5 g Signup and view all the answers

Which condition is crucial during stool sample collection?

Urine must not contaminate the stool sample. Signup and view all the answers

What should be included on the label of the specimen container?

Physician’s name and date of sample collection. Signup and view all the answers

Which parasitic stage is commonly found in Fasciola hepatica?

Cyst Signup and view all the answers

What should NOT be done when collecting a stool specimen?

Retrieve stool from toilet bowl water. Signup and view all the answers

What is the primary purpose of the flotation method in stool examination?

To increase the visibility of parasites Signup and view all the answers

Which component is NOT used in the flotation method for stool examination?

Ethyl esters Signup and view all the answers

What should be done after centrifuging the stool sample in the sedimentation method?

Remove the mass concentration at the bottom Signup and view all the answers

What is the recommended wait time for collecting stool samples after a patient has finished therapy with barium, bismuth, or mineral oil?

5 to 7 days Signup and view all the answers

How is the blood sample prepared for examination after spreading it on a slide?

It is fixed with methyl alcohol Signup and view all the answers

What is essential for mixing the stool sample in the flotation method?

Gentle agitation of the tube Signup and view all the answers

How many stool specimens are typically recommended for collection?

Three specimens over 10 days Signup and view all the answers

When should stool specimen collection be delayed for patients who have taken antibiotics?

2 weeks Signup and view all the answers

What is the appropriate time for centrifugation in the flotation method?

2 minutes Signup and view all the answers

What solution is added to the test tube after placing the stool sample in the sedimentation method?

Formalin solution Signup and view all the answers

What component is essential for examining liquid stool specimens?

Examination within 30 minutes Signup and view all the answers

Which of the following statements is true regarding the direct blood examination method?

The sample needs to dry at room temperature after fixation. Signup and view all the answers

What is a common method used in direct stool examination?

Macroscopic and microscopic examination Signup and view all the answers

What method is used to assist in the detection of parasites during microscopic examination?

Using stains such as iodine and hematoxylin Signup and view all the answers

What materials are needed to create a direct wet mount for stool examination?

Microscope slide, cover slide, stool sample, and a plastic pipette Signup and view all the answers

What should be avoided to ensure proper placement of the cover slide in a wet mount preparation?

Bubbles forming inside the sample Signup and view all the answers

What is one of the main reasons for preserving stool specimens?

To prevent the deterioration of any parasites present Signup and view all the answers

Which preservative is known to have a long shelf life and is suitable for both helminth eggs and protozoan cysts?

Formalin Signup and view all the answers

What is a disadvantage of using formalin as a preservative for stool specimens?

Permanent stained smears cannot be prepared from formalin preserved specimens Signup and view all the answers

Which preservative allows for good preservation of both protozoan cysts and trophozoites and has a long shelf life?

Sodium acetate acetic acid formalin (SAF) Signup and view all the answers

What is a common disadvantage of sodium acetate acetic acid formalin (SAF)?

It has poor adhesive properties Signup and view all the answers

What is a significant disadvantage of using Merthiolate Iodine Formalin (MIF) as a preservative?

It distorts protozoa Signup and view all the answers

Which statement is true about Polyvinyl Alcohol (PVA) as a preservative?

It serves as an adhesive for stool material Signup and view all the answers

Which two preservative types are noted for having a long shelf life?

SAF and PVA Signup and view all the answers

Study Notes

Parasitology

A parasite is a living organism that lives in or on another living organism (host) and benefits by obtaining food and shelter.
The host is the organism that provides the parasite with food and shelter.
The infective stage of the parasite is the stage that is capable of causing disease. This stage can be in the form of an ovum, larva, cyst, or adult.

Sample Collection

Stool samples should be collected in a clean, watertight container with a tight-fitting lid.
Urine should not be allowed to contaminate the stool specimen.
Stool should not be retrieved from toilet bowl water.
The specimen container should be labeled with the patient's name, identification number, physician's name, and the date and time of sample collection.
Stool samples from patients taking barium, bismuth, or mineral oil should be collected prior to or after therapy.
Stool samples from patients taking antibiotics or antimalarial medications should be delayed for 2 weeks.
The typical stool collection protocol consists of three specimens collected every other day or totaling three collected in 10 days.
Up to six specimens in 14 days are acceptable for diagnosing amebiasis.
Liquid specimens should be examined within 30 minutes of passage.

Laboratory Diagnosis

Direct examination is the most important laboratory diagnosis method because it is the primary method of identifying the parasite.
Direct stool examination involves macroscopic and microscopic examination.
Macroscopic examination involves assessing the stool's consistency, color, odor, and the presence of worms, mucus, pus, or blood.
Microscopic examination involves using normal saline, iodine solution, or hematoxylin stain to examine the parasite under a microscope.
Direct wet mounts and concentration methods are used for microscopic examination.

Direct Wet Mount

Materials used: Microscope slide, cover slide, stool sample, plastic pipette, stick.

Concentration Methods

Concentration methods are used when parasites are not readily visible in a direct wet mount but symptoms are continuous.
Concentration methods include flotation and sedimentation.

Flotation

Materials: Test tube, zinc sulfate solution, formalin, stool sample, plastic pipette, stick

Sedimentation

Materials: Test tube, formalin, saturated solution of NaOH, stool sample, absorbent, stick, slides, cover slips.

Direct Blood Examination

A drop of blood is placed on a clean slide and smeared with a spreader, creating a thin film.
The slide is washed with methyl alcohol and dried at room temperature.
Stains such as Leishman, Giemsa, or field stain are used to visualize parasites.

Preserving Stool Specimens

Preservatives are used to prevent the deterioration of parasites in stool specimens that are delayed in delivery or testing.

Formalin

Advantages: Suitable for helminth eggs, larvae, and protozoa cysts, used for sedimentation techniques, long shelf life, commercially available.
Disadvantages: Permanent stained smears not possible, trophozoites do not preserve well.

Sodium Acetate Acetic Acid Formalin (SAF)

Advantages: Good fixative for protozoa cysts and trophozoites, helminth eggs and larvae, easy to prepare, long shelf life, no mercury compounds, less toxic.
Disadvantages: Poor adhesive properties, permanent stains not optimal.

Polyvinyl Alcohol (PVA)

Advantages: Recommended for preserving trophozoite and cyst stages, serves as adhesive, long shelf life.
Disadvantages: Difficult to prepare in the lab, toxic (contains mercury compound).

Merthiolate Iodine Formalin (MIF)

Advantages: Easy preparation, good preservation and staining for most stages found in stool.
Disadvantages: Short shelf life, permanent stained smears not possible, iodine can distort protozoa.

Studying That Suits You

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

Description

This quiz covers key concepts in parasitology, focusing on the definition of parasites, their infective stages, and guidelines for proper sample collection. Understanding the importance of accurate sample handling is essential for effective diagnosis and treatment in parasitology.