[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 3 The Amebas
TABLE 3-3
Entamoeba hartmanni
Trophozoite: Typical
Characteristics at a Glance
TABLE 3-4
Entamoeba hartmanni Cyst:
Typical Characteristics at
a Glance
Parameter
Description
Size range 5-15 µm
Motility
Nonprogressive, finger-like
pseudopods
Number of nuclei One
Karyosome
Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm
Finely granular
Cytoplasmic inclusions Ingested bacteria may be
present
Parameter
Description
Size range 5-12 µm
Shape
Spherical
Number of nuclei One to four
Karyosome
Small and central
Peripheral chromatin Fine and evenly distributed
Cytoplasm
Finely granular
Cytoplasmic inclusions Chromatoid bars, rounded
ends in young cysts
Diffuse glycogen mass in
young cysts
Cytoplasm
Central
karyosome
Even
peripheral
chromatin
chromatin surrounding a small central karyosome,
as well as their variations, are consistent
with those of E. histolytica. The cysts of E. hartmanni
develop just as those of E. histolytica. A
diffuse glycogen mass and round-ended chromatoid
bars, similar to those seen in E. histolytica,
are typically seen in a finely granular cytoplasm
and are considered characteristic of young cysts.
Cyst wall
Size range: 5-12 m
Average size: 7-9 m
FIGURE 3-8 Entamoeba hartmanni cyst.
Diffuse
glycogen
mass
cytoplasm of E. hartmanni does not contain
ingested red blood cells.
Cysts. E. hartmanni cysts range in size from
5 to 12 µm, with an average size of 7 to 9 µm
(Fig. 3-8; Table 3-4). The spherical cysts may
have one, two, three, or four nuclei. Nuclei
located in the E. hartmanni cysts are characteristically
smaller in size than the single nucleus
of its corresponding trophozoite. The typical
nuclear structures of fine and even peripheral
Laboratory Diagnosis
Laboratory diagnosis is accomplished by examining
stool for E. hartmanni trophozoites and
cysts. It is important to note that the size ranges
of E. histolytica and E. hartmanni overlap. For
example, trophozoites that measure 12 µm and
cysts that measure 10 µm are within the size
range of both parasites. Specific identification
based only on size in such cases is impossible.
The protocol for reporting such findings varies
by laboratory. Proper use of the ocular micrometer
(see Chapter 2) is therefore essential to
obtain correct measurements of suspected
organisms.
Epidemiology
The geographic distribution of E. hartmanni is
cosmopolitan. The prevalence of E. hartmanni
appears to be similar to that of E. histolytica in