Medical Parasitology Lab Techniques
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Questions and Answers

What type of preparation is used to enhance the detail of protozoan cysts?

  • Concentration method
  • Colloidal preparation
  • Wet mount preparation
  • Direct saline wet preparation (correct)

    • What is the purpose of using Lugol's iodine or D'Antoni's formula in direct iodine wet preparation?

  • To aggregate parasites
  • To enhance the detail of protozoa (correct)
  • To remove small debris
  • To detect small numbers of parasites

    • What is the characteristic of mucus in a diarrheic stool?

  • Much mucus (correct)
  • Colloidal mucus
  • Homogenous mucus
  • Scanty mucus

    • What is the purpose of concentration methods in parasitology?

    <p>To detect small numbers of parasites</p> Signup and view all the answers

    What is the size of the coverslip used in direct saline wet preparation?

    <p>22mm</p> Signup and view all the answers

    What type of stool is characterized by scanty mucus?

    <p>Loose stool</p> Signup and view all the answers

    What is the amount of stool used in concentration methods?

    <p>2.5g</p> Signup and view all the answers

    What is the objective of concentration methods in parasitology?

    <p>To aggregate parasites</p> Signup and view all the answers

    What is the significance of the brown color of stool?

    <p>It is a result of the presence of bilirubin, a byproduct of heme in hemoglobin</p> Signup and view all the answers

    Which of the following is a disadvantage of using Modified Polyvinyl Alcohol (MPVA) in concentration methods?

    <p>It is more likely to be negatively affected if proper protocol is not followed</p> Signup and view all the answers

    What is the purpose of adding copper sulfate or zinc sulfate to Modified Polyvinyl Alcohol (MPVA)?

    <p>To provide better results for parasite identification</p> Signup and view all the answers

    What is a disadvantage of using Schaudinn's fixative (SF) in stool examination?

    <p>It is less suitable for concentration techniques</p> Signup and view all the answers

    Which of the following is a characteristic of Schaudinn's fixative (SF)?

    <p>It preserves morphologic protozoan, trophozoite, and cysts</p> Signup and view all the answers

    What is the limitation of using Modified Polyvinyl Alcohol (MPVA) in permanent stained smears?

    <p>It does not provide the same quality of preservation for adequate protozoan morphology</p> Signup and view all the answers

    What is the primary purpose of using Novy-MacNeal-Nicolle (NNN) medium?

    <p>For antibody and antigen detection</p> Signup and view all the answers

    What is the correct way to report the results of a parasite detection test?

    <p>By stating the scientific name (genus and species) of the parasite</p> Signup and view all the answers

    What type of staining is used for testing CSF?

    <p>Permanent staining</p> Signup and view all the answers

    What is the purpose of examining 10 fields in a sample?

    <p>To quantify the number of parasites present</p> Signup and view all the answers

    What type of fluids are examined for parasite detection?

    <p>CSF, blood, and other sterile fluids, such as fluids in cysts and peritoneal fluids</p> Signup and view all the answers

    Why is proper specimen selection and processing crucial in parasite detection?

    <p>To facilitate the detection of parasites</p> Signup and view all the answers

    What is the significance of a positive test result in parasite detection?

    <p>It indicates test infection</p> Signup and view all the answers

    Do bacteria need to be reported in parasite detection?

    <p>It depends on the protocol</p> Signup and view all the answers

    What is the purpose of centrifuging the specimen with zinc sulfate?

    <p>To remove fecal debris</p> Signup and view all the answers

    What is a disadvantage of using zinc sulfate in stool examination?

    <p>Some helminth eggs are too dense to float</p> Signup and view all the answers

    What is the purpose of using gauze in the procedure?

    <p>To strain the specimen to remove debris</p> Signup and view all the answers

    What is the purpose of permanent staining in parasitology?

    <p>To observe detailed features of protozoa</p> Signup and view all the answers

    What is the purpose of centrifugation in the procedure?

    <p>To remove fecal debris</p> Signup and view all the answers

    What is the advantage of using zinc sulfate in stool examination?

    <p>It yields cleaner preparation</p> Signup and view all the answers

    What is the minimum number of fields that must be reviewed before the slide can be considered negative?

    <p>300 fields</p> Signup and view all the answers

    What is the purpose of using iodine solution in the procedure?

    <p>To stain the parasites</p> Signup and view all the answers

    What is the primary purpose of the Kato Katz technique in areas with moderate to high transmission rates?

    <p>To assess the impact of control measures on the prevalence of STH infections</p> Signup and view all the answers

    What is the limitation of the Kato Katz technique in detecting parasitic infections?

    <p>It is not sensitive in detecting light-intensity infections</p> Signup and view all the answers

    What is the purpose of using a plastic spatula in the Kato Katz technique?

    <p>To scrape across the upper surface of the screen to sieve the fecal sample</p> Signup and view all the answers

    What is the purpose of applying a glycerol-soaked cellophane strip to the fecal sample on the microscope slide?

    <p>To enhance the visibility of parasite eggs</p> Signup and view all the answers

    In what type of surveys is the Kato Katz technique commonly used?

    <p>Surveys to assess the impact of control measures on STH infections</p> Signup and view all the answers

    What is the advantage of using the Kato Katz technique in epidemiological surveys?

    <p>It is simpler and more cost-effective than other diagnostic techniques</p> Signup and view all the answers

    What is the purpose of transferring a small amount of sieved fecal material to the hole of the template?

    <p>To fill the hole of the template and level with applicator sticks</p> Signup and view all the answers

    What is the recommended practice when removing the template from the microscope slide?

    <p>Remove the template carefully so that all the fecal material is left on the slide and none is left sticking to the template</p> Signup and view all the answers

    Study Notes

    Stool Examination

    • Stool color is important in indicating the condition: brown is normal due to bilirubin, a byproduct of heme in hemoglobin.

    Modified Polyvinyl Alcohol (MPVA)

    • Alternative to mercury-based PVA
    • Contains copper sulfate or zinc sulfate
    • Used in concentration methods and permanent stained smears
    • Disadvantages:
      • Does not provide the same quality of preservation for adequate protozoan morphology on a permanent stained slide as mercury-based fixatives
      • Parasite identification is difficult
      • More likely negatively affected if proper protocol is not followed

    Schaudinn's Fixative (SF)

    • Preserves morphologic protozoan, trophozoite, and cysts
    • Easy to prepare for permanent staining
    • Disadvantages:
      • Less suitable for concentration technique
      • Contains mercury chloride
      • Inadequate preservation of helminth eggs, larvae, coccidian, and microsporidia

    Stool Preparation and Examination

    • Direct iodine wet preparation: enhances detail of protozoan cysts
    • Direct saline wet preparation: enhances detail of protozoa
    • Concentration method: uses 2.5g of stool, purpose is to aggregate parasites and remove small debris
    • Novy-MacNeal-Nicolle (NNN) medium: used for the recovery of Leshamania spp.

    Reporting of Results

    • Should state scientific name (genus and species)
    • Ex: Entamoeba histolytica cyst seen

    Additional Infos

    • Is bacteria need to be reported? No, but it depends on the protocol
    • In general, most parasites are not quantified; amoeba-presence or absence is reported

    Specimen Processing and Laboratory Testing

    • Proper specimen selection and processing are crucial to parasite recovery
    • When zinc sulfate is added to the specimen and centrifuged, the parasites float to the surface and can be skimmed from the top of the tube
    • Advantage: more fecal debris is removed, making it easier for microscopic examination
    • Disadvantage: some helminth eggs are very dense and will not float, thus, some parasites will be missed

    Materials Needed

    • Gauze
    • Conical centrifuge tube (15mL)
    • Normal saline solution (0.85% / 10% formalin)
    • Centrifuge
    • Zinc sulfate solution
    • Disposable Pasteur pipette/bent wire loop/
    • Slides and coverslip
    • Iodine solution
    • Stool sample

    Procedure

    • Strain the 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 (1500rpm)
    • Decant the supernatant and repeat if necessary

    Permanent Stain

    • The use of stained slide preparation provides a permanent record of a patient's specimen and allows review by a consultant
    • Permanent stain is designed for analysis using the oil immersion objective (100x)
    • 300 fields must be reviewed before the slide can be considered negative
    • Designed to detect protozoan cyst and trophozoites
    • Staining allows to observe detailed features of protozoa by making its intracellular organelles visible

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    Description

    This quiz covers the laboratory techniques used in medical parasitology, including the use of Modified Polyvinyl Alcohol (MPVA) and the importance of stool color in diagnosis. It also touches on concentration methods and permanent stained smears.

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