LAB TEST 1 Flashcards
(55 cards)
What is the primary goal of diagnostic parasitology?
To identify any parasites present in a patient (human or animal).
What is the most common specimen for diagnosing intestinal parasitic infections?
Fecal samples.
Why is it important to collect fresh stool samples for examination?
To prevent degradation of trophozoites and ensure accurate diagnosis.
What are the two forms of protozoa seen in fecal samples?
Trophozoites (motile) and cysts (dormant).
What are the common methods used for fecal examination in parasitology?
Direct wet mount, fecal concentration, and permanent staining.
What is the purpose of a direct wet mount?
To detect motile trophozoites, cysts, helminth eggs, and larvae.
What is the function of iodine in direct wet mounts?
It stains cysts, making internal structures more visible.
What is the purpose of fecal concentration techniques?
To increase the likelihood of detecting parasites by removing debris and concentrating them.
What are the two main types of fecal concentration methods?
Sedimentation and flotation.
How does sedimentation concentration work?
It uses differences in specific gravity to allow parasites to settle at the bottom.
How does flotation concentration work?
It uses a solution with a high specific gravity, causing lighter parasite eggs and cysts to float.
What is the primary fixative used in stool preservation?
10% formalin.
Why is PVA (polyvinyl alcohol) used in stool preservation?
It preserves protozoan morphology for permanent staining.
What are the two main types of stains used in fecal parasite identification?
Trichrome stain and iron hematoxylin stain.
What is the advantage of using trichrome staining?
It provides good contrast and detail for protozoan cysts and trophozoites.
Why is iron hematoxylin staining used?
It gives excellent nuclear detail of protozoa.
What are the most common fecal artifacts mistaken for parasites?
Pollen grains, plant fibers, yeast, and fat globules.
How can yeast be differentiated from protozoan cysts?
Yeast is usually uniform in shape and size, whereas protozoan cysts have internal structures.
What is the best method to detect motile trophozoites in a fresh stool sample?
Direct wet mount with saline.
Why should multiple stool samples be examined for parasite detection?
Some parasites are shed intermittently, so a single sample may not be enough.
What are protozoa?
Single-celled eukaryotic organisms, many of which are parasitic.
What are the four major groups of protozoa based on movement?
Amoebae, flagellates, ciliates, and sporozoa (apicomplexa).
What are the two life cycle stages of protozoa?
Trophozoite (active, feeding stage) and cyst (dormant, resistant stage).
What is the causative agent of amoebic dysentery?
Entamoeba histolytica.
