[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 3 The Amebas
Quick Quiz! 3-29
Infections with Acanthamoeba species are encountered
in which of the following anatomical parts?
(Objective 3-5)
A. Eye
B. Large intestines
C. Lungs
D. Liver
Quick Quiz! 3-30
To prevent infection with Acanthamoeba species,
contact lens wearers should avoid which of the following?
(Objective 3-7C)
A. Strenuous exercise
B. Foods with high carbohydrate content
C. Wearing clothing made of cotton
D. Using homemade nonsterile saline solutions
LOOKING BACK
The typical characteristics that differentiate the
amebas include size, shape, nuclear structure,
cytoplasm appearance, and cytoplasmic inclusions.
These characteristics may best be compared
in the comparison drawings at the end of
this chapter: amebic trophozoites found in stool,
amebic cysts found in stool, and extraintestinal
amebic trophozoites and cysts.
It is important for clinicians to examine all
samples sent to the laboratory for parasitology
studies carefully. Suspicious amebic forms must
be evaluated closely, looking particularly for the
typical amebic characteristics. Composite drawings,
such as those provided in this chapter,
provide a useful resource and to aid in the identification
of and distinction between the amebas.
TEST YOUR KNOWLEDGE!
3-1. Match each of the key terms (column A)
with its corresponding definition (column
B). (Objective 3-1)
Column A
___ A. Ameba
___ B. Amebic
dysentery
___ C. Cyst
___ D. Encystation
___ E. Excystation
___ F. Karyosome
___ G. Pseudopod
___ H. Trophozoite
Column B
1. Transformation of a
trophozoite stage into
a cyst stage
2. Transformation of a
cyst stage into a
trophozoite stage
3. Amebic stage with a
thick cell wall
allowing for survival
of the organism in
the external
environment
4. A motile class of
Protozoa equipped
with pseudopods
5. Extension of
cytoplasm that aids
ameba in motility
6. Amebic stage
characterized by its
ability to move and
multiply
7. Small mass of
chromatin located
within the nucleus of
certain protozoan
parasites
8. An intestinal amebic
infection characterized
by blood and mucus
in the stool
3-2. Which of the following statements is not
true about amebic trophozoites? (Objective
3-1)
A. Trophozoites are delicate and motile.
B. Trophozoites are easily destroyed by
gastric juices.
C. Trophozoites are resistant to the environment
outside the host.
D. Replication occurs in the trophozoite
stage.
3-3. The ingestion of the infective __________
(cysts, trophozoites) completes the typical
intestinal amebic life cycle. (Objectives 3-1
and 3-5A)